BULGARIAN ACADEMY OF SCIENCES

 

CENTRAL LABORATORY
OF MINERALOGY AND CRYSTALLOGRAPHY

ANNUAL REPORT
No 14/2008

 

CONTENTS

Projects and topics # 16, 28, 29, 32, 33 and 35 are financially supported in part by the Bulgarian National Science Fund of the Ministry of Education and Science, Project # 35 – by the Sixth Framework Programme of EU, and Project # 13 – by the Bulgarian National Innovation Fund.

INTRODUCTION

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  TRENDS OF ACTIVITY:

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2. Structure and Staff

The whole range of operative activities of CLMC is organized in four structural units (three research departments and service laboratory department), administrative group and subsidiary staff. 

Organization chart of CLMC

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Laboratory of Electron Microscopy

Laboratory of X-ray Diffraction

• X-ray single crystal diffractometer Enraf Nonius 586 CAD4

• Two X-ray powder diffractometers DRON 3M with PC-based systems for phase identification

• Sspecialized data processing software, full ICDD database and structure databases ICSD, CSD, and PDB

Laboratory of Spectroscopy

• Bruker FT-IR spectrometer Tensor 37

• Varian UV-VIS spectrophotometer CARY-100 Scan

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• Home-made system for laser diagnostics

• AAS spectrometer Perkin-Elmer 330 B

• Laser microspectral analyser LMA-10

• ICP apparatus ARL 35 000 C

Laboratory of Thermochemistry:

• Differential scanning calorimeter DSC 1500 (Stanton Redcroft)

• Differential thermal analyzers STA 781 and DTA 675 (Stanton Redcroft)

• Thermomechanical analyzer TMA 790 (Stanton Redcroft)

Laboratories of Experimental Mineralogy and Crystal Growth

• Low temperature (up to 150^oC), low pressure (up to 5 MPa) hydrothermal crystallization

• Melt growth by the Bridgman-Stockbarger method (Crystalox)

• Flux growth

• Hot-pressing (up to 1500^oC, up to 100 MPa) (Crystallox)

• Furnaces of different type up to 1600^oC

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4. RESEARCH TOPICS

4.1 Mineral systems and mineral genesis

1. Eclogites from Maleshevska Mountain, SW Bulgaria (P. Nenova, N. Zidarov)

The eclogites under study crop out in the northern part of the Ograzhden Block of Serbo-Macedonian Massif, in Maleshevska Mountain [42]. They are hosted within a small body of gabbro-norites, which pass into gabbros and troctolites. That body is amphibolized in its peripherial parts and is hosted by two-mica gneisses of the Gneiss-Migmatitic Complex of Ograzhden Supergroup (Zagorčev, 1976).The eclogites form a small dyke-like steeply dipping body approximately 5 cm wide, which crosscuts the gabbroic rocks. Clasts of partly amphibolized banded eclogites were also found in this locality. Relict zones of partly developed eclogitization have been observed in the amphibolized gabbros. The eclogites of the dyke-like body are melanocratic, black-green, fine-crystalline rocks of massive to unclearly oriented structure. Their texture is nematogranoblastic and secondary symplectitic in respect to the decomposed alkaline pyroxene. Their mineral composition includes primary omphacite and garnet, and secondary clinopyroxenes (diopside and augite). Rutile, apatite, and ore mineral have also been observed. The banded eclogites are mesocratic, variegated in colour, middle-grained rocks of banded structure (an alternation of black-green and white bands). The white bands display granoblastic texture and are composed of quartz, zoisite, clinozoisite, and zircon. The dark bands have nematogranoblastic texture and are composed of garnet, alkaline clinopyroxene (symplectitically decomposed to diopside, augite, and plagioclase or amphibole and plagioclase), amphibole, quartz, ore mineral, rutile, zoisite, clinozoisite, and titanite. The alkaline clinopyroxene (aegirine-augite in the central parts of the grains and omphacite in the periphery), WoEnFs77.11–78.31Jd8.56–22.89Ae0–13.60, is grass-green and sized 0.2 ´ 0.5 mm to 0.3 ´ 1 mm. During the post-eclogitic metamorphic stage it has often been symplectitically decomposed to other clinopyroxene and plagioclase as well as to amphibole and plagioclase. The garnet is almandine with significant participation of grossular and pyrope component. It is euhedral, colorless to light pink-brownish and contains numerous small inclusions (amphibole, quartz, zoisite) in its central parts and displays transparent periphery. It has been formed during the prograde metamorphism.

The metamorphic products in the studied eclogites give evidence of two metamorphic stages. The products of the early stage (eclogitization) are the eclogites and eclogitized rocks. The products of the later stage are clinopyroxene, plagioclase, and amphibole. Clinopyroxene is represented by augite and diopside in symplectitic decomposition with plagioclase. The plagioclase is oligoclase (An15.5–23.4) both in the symplectites with clinopyroxenes as well as in the cross-fibrous crowns around garnet (An19.5). Plagioclase has also been observed as small, anhedral, clear lamellar crystals in the interstices of amphibole or having diablastic intergrowths with it. The amphibole in the reactionary crowns around garnet in eclogites is pargasite. Nematoblastic green crystals of high-aluminous ferrotschermakite have also been determined. The eclogitization has taken place in the temperature range of 500–750°C and pressure of 13.5–17 kbar. The amphibolitization has started at temperatures of 570–670°C and pressure of 12–13 kbar and has finished at about 600°C and 4 kbar. The presence of eclogites, eclogitized gabbroic rocks and garnet-containing orthoamphibolites formed on the eclogites are an evidence of high and ultrahigh pressure metamorphism of mafic rocks in eclogitic facies, followed by retrograde metamorphism in amphibolite facies within the Ograzhden Block. Probably, the eclogitization is a result of Cadomian, and the amphibolitization – of Hercinian tectonometamorphic events.

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2. Composition, texture and microstructural features of the agates from Madzharovo region, Eastern Rhodopes (B. Banushev, Z. Tsintsov, M. Sivilov)

The mineral composition, texture and microstructure of the agates and their host rocks from Madzharovo region, Eastern Rhodopes, are investigated. The agates have numerous attractive features and are of great interest for the jewellery industry. The rocks of Madzharovo region refer to the formation of the II intermediate acid volcanism – mainly volcanics (latites, shoshonites, rarely basalts) and pyroclastites. The agates are localized among hydrothermally altered volcanics (phenolatites). They are built of numerous rhythmically alternating bands with thickness of 1–2 mm of SiO₂ phases (quartz, chalcedony and quartzine), accompanied by inclusions of barite, sphalerite and galena. The phase inclusions in the agates are investigated by powder X-ray diffraction analysis as PDF-files of ICDD are used for comparison. The sense of the term “agate” is clarified. The genetic features of the agates are clarified and speculation regarding their relation with other occurrences in the Eastern Rhodopes is suggested [6].

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3. Late Alpine epithermal low-sulfidation electrum mineralizations in Kesebir Gneiss Dome, East Rhodope Mountain, SE Bulgaria (I. Marinova, P. Nenova).

Morphology of electrum from Khan Krum gold deposit, Krumovgrad Goldfield, SE Bulgaria was studied by SEM at magnifications ranging from 500 up to 10 000 times [34]. Electrum particles sized from 5 to 200 μm were examined. Part of them was obtained after crushing, milling and washing out of light minerals, and after dissolution of silicates with hydrofluoric acid. The other part was from freshly broken surfaces and from cross-cut sections. The electrum studied came from low-angle layer-like replacement pervasive silicification and from high-angle open-space filling veins of quartz-adularia composition and colloform-banded textures. Electrum particles from the layer-like pervasive silicification have deposited in microvoids and interstices of massive microcrystalline quartz. In the quartz interstices they have inherited their geometry. Their surface is smooth with numerous negative prints of quartz crystals (Fig.1, a). In open space in massive quartz they have formed botryoidal, globular, and wirelike aggregates without crystal faces having pores of 1–2 μm in diameter (or bigger) of oval and angular shape, and electrum globules of 0.3 to 2–5 μm in diameter on their surfaces.

Fig. 1. Morphology of electrum from the low-sulfidation Khan Krum gold deposit in SEM: a) electrum from the low-angle layer-like replacement pervasive silicification liberated from the embracing quartz by dissolution with HF; b, c, d) electrum from the high-angle colloform-banded quartz-adularia veins. Scale bar 10 μm; el – electrum

Electrum particles from the high-angle veins were observed in microcrystalline quartz-adularia bands. Electrum is abundant in the finest quartz-adularia bands (anhedral quartz and adularia grains of few microns, typically below 3–5 μm), which are darker and are vitreous-like in back scattered electrons in comparison with the neighboring electrum-poor, coarser microcrystalline quartz-adularia bands (Fig. 1b). It has formed botryoidal, globular, wirelike, branched and irregular aggregates without crystal faces (Fig.1c). In cross-cut sections the electrum aggregates exhibit numerous pores of oval and angular shape – 0.5–1 μm in diameter (Fig.1d). The final conclusion is that electrum from the high-angle veins has deposited under high and changeable supersaturation of hydrothermal fluids with respect to opal, quartz and adularia and upon non-equilibrium conditions as a result of intense boiling of fluids, whereas electrum from the low-angle layer-like pervasive silicification has deposited via weaker boiling. The preliminary data on the electrum mineralization in Skalak occurrence, Krumovgrad Goldfield, East Rhodope Mountain, SE Bulgaria revealed that the hydrothermal fluids have formed quartz-adularia-sericite-pyrite assemblage of ore-associated alteration and ore bodies composed mainly of massive microcrystalline quartz and scarce amounts of micron-sized adularia, sericite, pyrite, marcasite, and electrum [36]. In this work, the Skalak occurrence was classified as an epithermal, low-sulfidation, and adularia-sericite type electrum mineralization. The low amount of adularia, the low distribution of bladed quartz textures, the presence of siliceous sinter, and the absence of colloform banded textures are indicative for high levels of the hydrothermal system, above the level of intense boiling of fluids.

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4. Alteration of monazite in the Igralishte granite pluton, Southwestern Bulgaria (M. Tarassov, E. Tarassova, I. Piroeva)

In the last decade significant efforts have been made by a number of researchers for investigation of stability of monazite – (Ce, La, Th)PO₄, during fluid-rock interactions due to the exclusive importance of the mineral as a repository of REE and Th in the continental crust; as a unique object for Th-U-Pb geochronology, geothermometry, and geochemistry; as a potential structural form for preservation of nuclear wastes. The object of the present study is monazite with well pronounced signs of postmagmatic alteration from the Igralishte granite pluton (Ograzhden block of SMM) [56, 58]. Typical microtexture of the monazite replacement includes central relic monazite core followed by zone of pseudomorphic aggregate of poorly crystallized britholite-rich apatite and then by outer mantle of epidote. Two types of monazite particles were found during TEM examination: the first one represents intact mineral grains related to relic forms of monazite and giving selected area electron diffraction (SAED) patterns typical for monocrystal material; the second one is presented by clearly polycrystalline aggregates which SAED patterns show spot reflections grouped in rings. The obtained SAED patterns of several [uvw] zones of the intact monazite demonstrate sharp reflections thus indicating that despite the respective age (~245 Ma) and the significant content of Th (ThO₂ – up to 10 wt.%) the mineral exhibits no apparent signs of metamictization. The performed EPMA in TEM evidences that the content of principle elements as LREE and P in both varieties of monazite are almost the same. More significant differences have been observed in the content of Si, Y, Th, U, and Ca which are notably higher in the polycrystalline monazite. The inspection of series of particles of the polycrystalline monazite allows to assuming that they are not composed of randomly oriented domains. This fact is well illustrated by a case particle which polycrystalline SAED pattern actually presents superposition of series of slightly rotated and/or inclined SAED patterns originated from one and the same [211] zone. The domains (with prevailing size of 10–20 nm) of this particle demonstrate characteristic Moiré fringes with spacing of ~2.0 and 4.5 nm related to (120) and (011) atomic planes of monazite with angular rotation of 4–9°. The obtained results allow suggesting that the observed microstructure of the polycrystalline monazite is a manifestation of original mosaic microstructure of the mineral, however influenced by later alteration processes. Most probably the found out altered monazite represents an intermediate state of the mineral in the course of its alteration into the secondary pseudomorphic material.

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5. Mn-rich norsethite from Kremikovtsi ore deposit (N. Zidarov, O. Petrov, M. Tarassov, Z. Damyanov, E. Tarassova, V. Petkova, Yu. Kalvachev, Z. Zlatev)

Norsethite, BaMg(CO₃)₂ is a mineral from the dolomite group, which is formed under different geological conditions – in sedimentary and hydrothermal deposits as well as in carbonatite complexes. Norsethite was mentioned for the first time in the Bulgarian geological literature in the list of supergene minerals found in the Kremikovtsi deposit (Damyanov et al., 1996).
The purpose of this study is characterization of the properties of Mn-rich norsethite [81].

Occurrence. Kremikovtsi ore deposit situated some 15 km NE of Sofia town, at an altitude of about 400 m.
Geological setting. The Kremikovtsi ore deposit was defined as a zonal car-bonate-hosted sedimentary exhalative iron (+Mn)–barite–sulfide deposit of SEDEX type (Damyanov, 1999). More than 92 minerals and mineral varieties were encountered for the three stages of formation of this deposit: sedimentary-hydrothermal, hydrothermal-metasomatic and supergene (Damyanov et al., 1996). The deposit has been exploited for more than 50 years mining iron ore and barite.

Norsethite aggregates. In the voids within diagenetic Mg-Mn siderite on a spherosiderite crust there are developed aggregates of Mn-rich norsethite, among which we can differentiate the following types: complex aggregates built by packets of fine platy crystals flattened on {0001} (Fig. 1); sub-parallel aggregates of long prismatic crystals ending with sharp rhombohedra, which have faces c {0001}, m{1010}and a{1120}; clusters of needle prismatic crystals terminated by very sharp rhombohedra; spherulite aggregates with radiaxial fibrous structure (Fig. 2).

Associated minerals.The Mn-rich norsethite occupies small cavities in diagenetic Mg-Mn siderite II-type. The cavities are usually incrusted by fine-crusted aggregates of “spherosiderite”, the grains of which have spheroid shape and consist of many regularly intergrown rhombohedral subcrystals of Ca-Mg rich siderite. Metacrysts of Ca-Mg-rich rhodochrosite and Mg-poor calcite have developed in and along the borders of the Mn-rich norsethite aggregates. Chalcopyrite is developed around grains of rhodochrosite that are incorporated in Mn-rich norsethite. Native copper grains are also presented. Barite is found in small nests and veinlets. Small rhombohedral calcite crystals have deposited over the supergene alteration products (Feand Mn-oxides) of siderite.

Chemical composition. Averaged microprobe analysis of 9 measurements gives (wt.%) BaO – 53.11, MgO – 11.28, MnO – 4.68, all that corresponding to the empirical formula Ba_1.00Mg_0.81Mn_0.19(CO₃)₂. The presence of [CO₃]^2– groups in the composition of the mineral is evidenced by FTIR data. Ca, Mn and Fe bearing varieties of norsethite can be distinguished as well.

Fig. 1. Complex aggregates of Mn-rich Fig. 2. Spherulite aggregates of Mn-rich norsethite norsethite

XRD data.The mineral is trigonal, space group R3m . The unit cell parameters for space group R3m are: a = 5.0318(11) Å, c = 16.8705(15) Å, V = 369.01(3) ų, z = 3. The strongest observed reflections in the powder diffraction pattern are (d in Å, I observed): 5.629, 38; 3.871, 28; 3.026, 100; 2.109, 25; 1.897, 29; 1.875, 30. The unit cell parameters are slightly bigger than those of norsethite not containing Mn, due to the bigger ionic radius of Mn²⁺ (0.83 Å) with respect to Mg²⁺ (0.72 Å). There are slight changes in the peak intensities due to the greater atomic scattering factor of Mn compared to Mg.

Physical and optical properties. The color of Mn-rich norsethite is pale yellow or it is colorless, transparent, with vitreous luster. Optical class – uniaxial (–), n_ω = 1.698, n_ε = 1.527, δ_max = 0.171. Photoluminescence under ultraviolet irradiation with λ = 366 nm is in weak dark red color, which converts to more brightly brownish red one when irradiation is with λ = 254 nm.

Infrared spectroscopic data. Several bands characteristic for carbonate group are observed in the FTIR spectrum (Fig. 3): at 1452 and 1114 cm^–1 arising from stretching vibrations of C–O; at 880 and 696 cm^–1 assigned to out-of-plane and in-plane bending mode of the (CO₃)₂-ion; and combinations of internal mode frequencies with a lattice mode occurring at 2530 and 2649 cm^–1.

Fig. 3. FTIR spectrum of Mn-rich norsethite

DTA-DTG-TG data. The thermal behavior and mass loss of the Mn-rich norsethite are experimentally investigated (Fig. 4). Important temperature regions are: 556–776°C (destruction of the crystal structure of the mineral); 820–840°C (phase transformation of the newly formed BaCO3) and 930–1100°C (formation of liquid phase resulting from eutectic reaction at 1038°C).

Mineral forming conditions. The paragenetic analysis shows that norsethite and the associated carbonate minerals have been deposited from hydrogen-carbonate solutions containing Ba²⁺, Mg²⁺, Mn²⁺, and HCO₃^2– ions resulted from the dissolution of Mg-Mn-rich siderite and barite from the host ores, in a closed system with respect to CO₂, at pH between ~6 and ~10 and under reduction conditions. The formation of splitted crystals of siderite and spherulite aggregates of norsethite indicates uneven concentration distribution, however, high oversaturation of the solutions. Autometasomatic processes have led to formation of metacrysts of Ca-Mgrich rhodochrosite and Mg-poor calcite among norsethite crystals.

Fig. 4. TG-DTG-DTA curves of thermal decomposition of Mn-rich norsethite

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6. Ontogenetic investigations on hematite inclusions in amethyst from Vitosha Mountain (O. Vitov)

Preliminary results from the study of amethysts with hematite platelets and whisker inclusions from Vitosha Mountain, Western Bulgaria, from the area between the villages of Marchaevo and Rudartsi were presented [67]. Spectral and powder XRD analyses on amethysts’ samples have been done and the hematite inclusions have been investigated by the Debye-Scherer method. Adiagnostic etching with sodium bicarbonate has been performed on orientated thin sections sealed in autoclave. The study of the temperature of homogenization of the gas-liquid inclusions in quartz slices perpendicular to the c-axis has pointed out to increase of the solution temperatures. The study gives evidence for the heating of the monzonite intrusion during the process of syenite intruding and short-term heating during the process of pegmatite intruding. The simultaneous growth of quartz and hematite evidences the neutrality of the hydrothermal solutions in strongly oxidizing environment and the presence of a geochemical barrier – an indication for searching of uranium-bearing deposits in the area.

Fig. 1. Amethyst crystal from Vitosha Mountain and changes of the temperature of homogenization of the gas-liquid inclusions in it. The scepter shape of the crystals is explained with the increase of the temperatures of the hydrothermal solutions upon the intrusion of the syenite portion of the pluton.

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7. Genetic information on fluorite and its applicability (B. Zidarova)

In minerals, information is encrypted not only on the environmental conditions during their formation, but also on the conditions required for growing crystals from them. That makes it suitable for both genetic studies and technological purposes. Such an approach is applied to fluorite from Slavyanka deposit in SW Bulgaria. A topographic mineralogical mapping is performed taking into account the character of the X-ray luminescence spectra in order to delineate the borders of the geological bodies containing diverse varieties of fluorite suitable for producing optical grade single crystals. By comparing the optical absorption of the raw fluorite and that of single crystals grown from it, we were able to conclude that (1) the thermal luminescence spectra are informative for the radiation stability, (2) the emission spectra indicate the content of structural admixtures (REE) that would hinder the crystal applicability, (3) the emission spectra can also be used for controlling the homogeneity of the raw material and the process of growth, (4) the infrared spectra are characteristic of each fluorite variety and thus can be used for preparing the raw material for crystal growth. The correlation between the content of Ce in the raw fluorite and the optical absorption coefficient of Ce2+ at 360 nm in the synthesized single crystals could be used as an express method for preliminary determination of their quality. The variety of methods that could be used for determination of the optical quality of the synthetic fluorite single crystals (X-ray luminescence, thermal luminescence, emission and infrared absorption spectroscopy) provide different levels of information for reliability of prognostic estimation. An important characteristic of the IIc variety is the very low content or even the absence of REE that could be explained by the purification of the solutions from REE parallel to the front of mineral formation. Thus, one can conclude that optical details of a proper properties in the infrared and visible spectral ranges can be studied on the basis of the fluorite structure and its genetic properties [78].

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8. Distribution of phosphate minerals in alluvial sediments in Montana District, Northwestern Bulgaria (O. Vitov)

Data collected and elaborated to produce probability map and double Fourier series model of distribution of phosphate minerals like xenotime, monazite, apatite, and pyromorphite from stream-sediment pan-concentrated samples taken in Montana District, NW Bulgaria, were presented [70, 158]. The results obtained revealed that monazite and xenotime from stream-sediment haloes are concentrated in the western-northwestern part of the district whereas apatite predominates in the southeastern part along the boundary between a Paleozoic granite intrusion and transgressive Permian and Lower Triassic sediments. The stream-sediment haloes of pyromorphite in the Martinovo-Chiprovtsi Ore Region are not spatially related to the haloes of other phosphates. The compiled graphs of statistical correlations confirm this tendency. On the basis of the outcomes a hypothesis for the pyrogenetic origin (forest fires in the oxidation zone of the lead-sulphidic deposits) of phosphorus in the found pyromorphite has been proposed.

Fig. 1. Distribution of the phosphate and lead ore deposits and occurrences in Montana District, Western Bulgaria (A); model of the phosphate evolution in Nature (B)

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9. Lead in stream-sediment pan-concentrated samples from Bulgaria (O. Vitov)

The mineral composition of Bulgarian alluvial sands was investigated. 132 739 stream-sediment pan-concentrated samples were collected containing rock-forming, ore, and supergene minerals. Presence of lead was documented in 2278 stream sediment sampling protocols. The spatial distribution of lead was presented by maps based on the frequency of occurrence, a Fourier model, and a map of the strongest harmonics. The minerals, which correlate with lead in the alluvial sediments, were determined using statistical approach. These are lead-containing minerals, products of their supergene transformation, and particular rock-forming minerals. A tendency for discovering of lead in the vicinity of known base-metal deposits was established. The study carried out showed that discovering of lead in the stream sediments is a reliable indicator for lead-containing prospects and for soil pollution with lead and lead compounds. A pyrogenetic type of mineral formation in Nature has been defined – minerals formed during or in relation with forest fires. The peculiarities of this genetic type were investigated on the example of distribution of lead [69, 156] and pyromorphite [70, 158] (Montana district). A hypothesis has been proposed concerning the circle of phosphorus in Nature including the pyrogenetic factor (Fig. 1, B).

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10. Interpolation model of gold distribution in the water catchment basins of Struma and Mesta Rivers, Southwestern Bulgaria, and extrapolation model for the Republic of Macedonia (O. Vitov)

Interpolation and extrapolation double Fourier series models of gold distribution in Bulgaria and Republic of Macedonia were presented [68, 157]. 34405 pan-concentrated stream-sediment samples collected with a density of 2.7 samples/km² within the water catchment basins of Struma and Mesta Rivers on Bulgarian territory comprising Pernik, Kyustendil and Blaboevgrad districts, were analyzed. The minerals which correlate positively and negatively with gold and those which do not correlate were determined. The frequency of gold in the stream-sediment samples was assumed to be a probability for discovering of gold in the area and contour maps of probability for gold finding were compiled using double Fourier series. The interpolation double Fourier series model shows that the probability distribution for gold finding has a stripe pattern as the highest probabilities are concentrated in three stripes named after the towns falling there as follows: Tran-Radomir-Dren, Treklyano-Kyustendil, and Yakoruda-Gotse Delchev. All known gold deposits, occurrences and indications fall into these stripes which points to the good effectiveness of the applied model. The extrapolation double Fourier series model was applied for the territory of Republic of Macedonia. The grid of the model is a square of 35 km². The parameters of the model have been verified statistically and it has been ascertained that the model is consistent with the data. The major harmonics of probability distribution of gold having indexes (2.2) includes 35% of the gold and points to gold prospects in Northeastern and Southwestern Macedonia. Other harmonics of probability distribution of gold having indexes (3.2) concentrate 18% of the gold and allow us to prognosticate gold deposits in Central Macedonia. The stripe pattern of gold distribution in Western Bulgaria and in Macedonia is attributed to the pronounced anomaly of Moho boundary in the Central Balkan Peninsula.

Fig. 1. Frequency of gold in stream-sediment samples from the water catchment basins of Struma and Mesta Rivers – Southwestern Bulgaria (A); The most pronounced regularity of its distribution – interpolation model (B, double Fourier model, 35% of the gold falls within the stripes that strike 135° and crosswise).

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11. Mineralogical dividing and prognoses for prospecting of mineral resources in Pernik, Kyustendil and Blagoevgrad districts, Western Bulgaria (O. Vitov).

A territory of 12 700 km² comprising the water catchment basins of Struma and Mesta Rivers in Bulgaria was studied [99]. Data for the mineral composition of 34 405 pan-concentrated stream-sediment samples taken from the National Geofund of the Ministry of Environment and Waters were analyzed. The sampling was performed with a density of 2.7 samples/km². The territory studied was divided into 1027 squares each one of about 12 km² in area and probability maps for discovering of various minerals were compiled. The work presents an evaluation of the density of stream-sediment sampling, mineralogical dividing, and prognoses of prospecting for gold, cinnabar, galena, bismutite, chromite, columbite, and other mineralizations. Interpolation modeling of the mineral fields showed a regular arrangement of the mineral halos of mechanical dispersion into major bands of 135° strike and smaller not so well distinguished bands of 45° strike. Mineral deposits, occurrences, and indications can be found in the places of intersection of these bands. The outlined halos of mechanical dispersion of the ore minerals and the products of their supergene alteration within the water catchment basins of Struma and Mesta Rivers on the territory of Bulgaria provide evidence for mercury, base metal, gold, and rare earth element deposits. These halos are complex mineral anomalies manifested on the territories of the known Osogovo and Tran Ore Regions as well as anomalies in regions of unclear prospectivity, arranged into bands as follows: Tran-Radomir-Dren-Yakoruda-Gotse Delchev-Dospat and Treklyano-Kyustendil-Vlahina Mountain and southeasterly. The comparison between the revealed regularities of mineral distributions based on stream-sediment sampling and the anomaly of Moho boundary in the region were discussed. It has been shown that the samples taken in places where the thicknesses of Earth crust change have richer mineral composition. This is indicative for the way the mechanism of mineral genesis in the studied region is related to the processes acted between the Earth crust and the mantle.

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4.2 Environmental and technogenic mineralogy

12. Mineralogy, geochemistry and environmentally safety application of solid fuels and their combustion and pyrolysis products (S. Vassilev, Ch. Vassileva)

Some problems and perspectives concerning the effective and environmentally safety treatment of the municipal solid wastes (MSW) in Bulgaria are discussed and summarized [63]. The various methods for MSW processing worldwide are discussed and their advantages and disadvantages are pointed, as well as their applicability in Bulgaria. The trace elements contents in the MSW are also elucidated. A new approach for the combined chemical and mineral classification of the inorganic matter in coal is introduced and evaluated. Thirty-seven coal samples from Australia, Bulgaria, USA, Japan, Canada, South Africa, China, Spain, and Ukraine, which differ considerably in their geology, rank, age, ash yield, chemistry and mineralogy, were used to establish the classifications [65]. The chemical classification system was organized according to the contents and significant positive or negative correlations of ash-forming elements in coal ashes using three composition-based criteria, namely: (1) sum of Si, Al, K, and Ti oxides;(2) sum of Ca, Mg, S, and Na oxides; and (3) Fe oxide. This approach resulted in four chemical coal ash types (sialic, calsialic, ferrisialic, and ferricalsialic) further divided into seven subtypes (with high, medium and low acid tendencies) based on the sum of Si, Al, K, and Ti
oxides. The more important mineral classification system was organized according to the contents, genesis, and behaviour of mineral classes and species in coals also using three composition-based criteria, namely: (1) silicates + oxyhydroxides; (2) carbonates; and (3) sulphides + sulphates + phosphates. This approach resulted in four mineral coal types (silicate, silicate–carbonate, silicate–sulphide, and silicate–sulphide–carbonate or mixed) further divided into seven subtypes (with high, medium and low detrital tendencies) based on the sum of silicates and oxyhydrox ides. The chemical and mineral coal types and subtypes were characterized and relationships and distinctions between them were also described. The benefit of the new classification approach is the use of significant correlations and actual element associations, and well-defined and genetically described mineral classes and species in coal.

Potential applications of the above chemically and mineralogically categorized coal types and subtypes were discussed [64]. The advantage of the proposed classification systems is the identification and implementation of significant relationships between concentrations of elements, combined chemical and mineral associations, and a genetic approach for differentiation of minerals. The data have shown that various applications and technological problems concerning coal, such as correlation of different coals, prospecting and recovery of valuable compounds, coal preparation, combustion performance, prediction of combustion residues, slagging, abrasion, and corrosion, are related directly or indirectly to specific mineralogically and chemically categorized coal types and subtypes. Furthermore, some environmental risks and health concerns of coal use, namely acid-mine drainage, mobilization of water-soluble trace elements, volatilization of hazardous elements, and certain diseases also may be connected with specific mineral and chemical coal types and subtypes. A concept of ‘‘self-cleaning fuels” was also introduced and developed based on mineral coal types. This concept emphasizes that the retention of volatile hazardous elements in power plants, namely depressed volatilization and increased capture and immobilisation, can be achieved by: certain originally present minerals and organic ingredients in the fuel; some newly formed inorganic phases and chars during fuel combustion; selected mineral additives to the fuel; or selectively blended fuels such as specific coal types with other fuels.

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13. Development of technology for combined gold extraction from copper ores (I. Donchev, I. Baltov, M. Tarassov)

The result from the laboratory and experimental-industrial investigations is the development of proposed for implementation technology for further extraction of gold from the porphyry copper ores of Asarel deposit. The technology consists of a combination of the known gravitational and flotation dressing. Beside the ensuring higher financial performance, it includes technical solutions and parameters that are new in the dressing of gold-containing ores. In the final experiments conducted in industrial conditions is obtained gravitational final concentrate with a high gold content.The nature, distribution, and mineral composition of the products obtained in industrial tests using centrifugal concentrator “Knelsson” have been analyzed. These products present a good possibility to establish the specific quantitative features of the havy minerals and particularly of the gold particles. The samples have been sifted into three grades: + 0.08 mm, –0.08 +0.04 mm, and –0.04 mm. Two artificial polished sections have been worked out of each grade and mineragraphically investigated by polarized light microscopy using “Leitz-Orthoplan” microscope. An integrationtable has been used to count the mineral grains. Microphotographs of gold and other heavy minerals have been taken by digital optical camera “Olympus”. Selected as most typical by form, size, and optical characteristics gold from the products has been investigated by means of electron probe microanalysis to determine its grade and intergrowth with other minerals from the sink, as well. These results were used for the production of “Atlas of gold from the sink obtained in industrial tests in “Asarel” JSCo with centrifugal concentrator “Knelson”.

Fig. 1. Gold distribution by size in mm: white – along width; gray – along length

Plenty of gold has been observed in the three grades. There are three types of gold – rich yellow, pale yellow, and gold considered to be close to electrum. The gold content is highest in the sink of the grade –0.04 mm. After the initial observations made in reflected light and according to the so far known morphometric classifications the following division of the various types of gold particles has been adopted (Fig. 1):

The gold particles have been divided into three groups depending on the admixtures presented – high-grade (over 90% Au); medium-grade (80–90% Au), and low-grade (below 80% Au), close to electrum. The admixtures are: Ag in all cases, Cu in most of the cases and Fe – rarely.

Fig. 2. Grade –0.08 +0.04 mm. Gold-pyrite aggregate. The pyrite occupies about 1/3 of the surface of the grain’s visible part. Gold size –0.07´0.06 mm. Gold analysis, mass%: Au – 99.24%, Ag – 1.36%, total 100.59%. SEM, ´ 1250.

About 30% of the gold is presented by non exposed grains and it is met in the form of aggregates with other ore minerals. The biggest part of it (about 35–40%) is included in pyrite (Fig. 2), less than this forms intergrowths with tennantite, bornite, covellite, and chalcosine. Intergrowths with chalcopyrite have been observed only in a couple of aggregates (Fig. 3).

Fig. 3. Grade –0.04 mm. Gold inclusion in goldchalcopyrite aggregate. Size –0.05´0.035 mm. Gold analysis indicated by black dot, mass%: Au – 97.86%, Ag – 0.13%, Fe – 0.71%, Cu – 0.72%, total – 99.42%. SEM, ´1150.

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14. Mineralogical-technological aspects of the ore petrography of porphyry copper deposit Elatsite (I. Donchev, S. Encheva)

The mineralogical-technological investigations play the linking role between mineral composition, ores’ textural and structural characteristics and the technological schemes of processing specific for each concentration plant. Therefore, the order of carrying out such like scientific applied works is in general as follows: examining the petrography of the ore-hosting rocks, investigation of the microstructural features of the ores, as the accent is put on the technological characteristics of the minerals and realizing of reverse link for impact – from the established characteristics of the processed plant products to the ore preparation – crushing, milling and classification. The sampling ores from the open pit of the porphyry copper deposit Elatsite are the object of this investigation. Basic attention is paid to these ones from levels 1180, 1195, 1210, and 1225 m (for massive and porphyry rocks) and 1345 and 1360 m (for contact-metamorphic rocks), which carry a wealth of mineralogical–petrographic information. The samples are collected into the pit at the working places of the diggers from the corresponding geologic blocks. In addition, during the years of exploitation of “Mirkovo” Flotation Plant regular samplings have been carried out comprising the ores preparatory operations and the flotation and these data are taken into consideration in the present work [10, 106].

1. Petrographic investigations. In the open pit “Elatsite” granitoids, dykes, xenoliths, contact metamorphized rocks and rocks of DPC (Diabase Philitoid Complex) occur. The granitoids are leucocratic to mesocratic, light-gray in color, with pale-pink shade at some places. The granodiorites are medium- to coarse-grained, often porphyritic in K-feldspar. Their structure is massive, and the texture is mainly hypidiomorphic, and in some sections it is monzonite, characterized by corrosion and resorption of plagioclase and K-feldspar. The dyke formation is presented by porphyritic rocks with granodiorite-porphyry and granosyenite to quartz-monzonite composition. The porphyry generation is presented by plagioclase, mafic minerals – amphibole and biotite, and to a less extent – K-feldspar. The texture is allotriomorphic. The contact-metamorphic rocks in the region of Elatsite deposit consist mainly of hornfels and hornfels schists with or without andalusite and corundum. They are compact, meso- to melanocratic rocks of dark-ashy color. The structure is predominantly microgranolepidoblastic to porphyroblastic in andalusite. They pass gradually into the rocks of DPC. The xenoliths are quite widespread bodies of various size hosted by the Vezhen and Elatsite plutons. They are characterized by dark gray color, massive, fine-grained structure, and porphyritic texture. Judging on the newly formed mineralogical assemblages it can be concluded that the xenoliths’ initial composition has been much more basic and subsequently they have transformed into rocks of diorite composition.

2. Mineralogical-technological investigations of the hydrothermal mineraization. A great number of studies were devoted on the geology, structural position, mineralogy, and geochemistry of Elatsite deposit (Bogdanov, 1987; Dimitrov, 1988; Tokmak chieva, 1981; Georgiev, 2004). The secondary alterations of the primary ore mineralization – the secondary enrichment zones, characterized by the formation of rich in copper sulphides and the oxidation zones of the deposit complicate the geological and mining situation. The original petrographic textures and structures have been obliterated thus provoking difficulties for the ore preparation and flotation.

Fig. 1. Grain size of the copper minerals from the massive rocks (right) and from the metamorphites (left).

The mineralogical-technological investigations of the ores from Elatsite deposit have revealed that the porphyry copper mineralization within the massive rocks and that one within the metamorphites differ from each other by their textural characteristics, the ore mineral size, and the degree of exposure. They have been used to determine the efficiency of metal extraction from the concentrate and the losses within the waste (Iliev, Donchev, 2006). The numerous determinations of the size of the impregnated chalcopyrite and another copper and copper-iron sulphides grains within the both types of host-rocks have revealed that within the schists the grains are much finer, and within the massive – much coarser as the amount of the grains over 0.06 mm in size prevails. The major part (about 80%) within the schists reaches size up to 0.05 mm and within the massive and the porphyritic rocks the size of 80% of the copper minerals’ aggregates falls within the range 0.015–0.06 mm and over this value (Fig. 1). The grains within the granodiorites and the porphyries are coarser and evenly distributed within the different grades as shown on the histogram. Special attention has been paid to the content of solid minerals within the rocks that have been affected by contact alterations – andalusite- and corundum-containing schists and hornfelses. The corundum has been ascertained by powder XRD analysis and has been detected by means of optical and scanning electron microscopy. In some polished sections its content is over 5%. Both types of rocks differ substantially. The granodiorites, quartz-monzodiorites, and microdiorite porphyries can be milled more efficiently, in contrast to the metamorphized rocks because the andalusite and the corundum raise the expenses for the milling bodies and increase the milling duration till the required grade is achieved. Based on the numerous technological experiments conducted during the past years, the expedience of feeding the oredressing plant with mixture of granodiorites and schists in ratio 3:1 has been found out.

The mineralogical-technological investigations of the ores from Elatsite deposit during the past years have justified the advisability of their conducting because they have:

– contributed to study in detail the petrography of both types of ore-hosting rocks, thus providing explanation for some differences in the behavior of the ore and gangue minerals in them in the process of ore preparation;
– cleared the differences of the microstructures of both types of ore-hosting rocks;
– revealed the basic regularity in the degree of liberation of the copper minerals in the processes of grinding and grading;
– facilitated the determination of the optimal technological conditions in the
ore-dressing plant thus contributing to the increase of the economic indicators.

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15. Application of the sequential extraction procedure for speciation of some trace elements in sediments and dump materials from East Maritza Basin, Bulgaria (Z. Milakovska, N. Lihareva)

Studies on the elements fractionation among the mineral phases in shales, mud rocks and clayey rocks are rare because of the fine grain-size structure and difficulties to separate discrete mineral fractions. Microprobe analysis gives information on the content of main elements only, not about the forms of the element present, e.g. adsorbed, isomorphic or organic. The selective or single extraction procedures can help in studying such a kind of fine sediments and estimating the ion mobility under different environmental conditions. On the other hand, clay sediments are interesting for studying because of their good “accumulative properties” with respect to trace elements. The study is a first attempt to apply the sequential extraction procedure to separate the main components in clay sediments and dump materials from East Maritza Basin (EMB) by their composition [40, 134].

The selection of samples is based on their position and trace element content: two core samples of black clays (C-69-56 and C-3-14), two from internal dumps – black and gray-green clays (1998bl and 1998gr) and two from external dumps – mixed gray-green (SSm) and ochreous clays (G-2) from Troyanovo-2 mine (EMB). They are composed mainly of clay minerals (mixed layer illite/smectite, illite, and kaolinite group minerals), quartz, and of small amounts of gypsum, feldspar, and pyrite. Organic matter is a component in the black clay types only. The content of the organic carbon (Corg) varies from 0.39 to 2.35%. The selective sequential extraction procedure used is based mainly on the scheme proposed by Tessier et al. (1979) and Ure et al. (1993). It consists of the following extraction steps and operationally determined fractions: 1. Water-soluble forms removed by deionized water; 2. Exchangeable cations extracted in 1M magnesium chloride solution; 3. Carbonate fraction – acid soluble forms in 1M ammonium acetate at pH = 5; 4. Reducible forms associated with oxides and hydroxides of Fe, Mn and Al extracted in 0,1M NH2OH.HCl at pH=2; 5. Oxidizable forms associated with organic matter and sulphides by a consecutive treatment with H2O2 (pH = 2–3) ammonium acetate at pH = 2; 6. Residual fraction forms associated with silicates. The percentage elemental distribution according to the chemical analysis of the sequentially leached fractions is given in Fig. 1.

Fig. 1

Generally, the observed features of the elemental distribution are: 1) the content of the majority of traced elements maximizes in the residual associated with the silicates fraction; copper and chromium are connected also with fraction V and sporadically with fraction III; vanadium and aluminum are similar in that they have some accidental oxidizable, water-soluble and carbonate forms of presence; cobalt, zinc, and nickel are irregularly distributed in all the fractions studied; 2) lead differs from the other elements in that it is present mainly in the carbonate and sulphide
and organic matter fractions, but not in the water-soluble, oxidizable and silicate fractions; 3) molybdenum is also an element with specific features – it was found in high amounts only in fraction V, and sporadically in fractions III and V.

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4.3. Archaeomineralogy

16. Distribution and typifying of gold artifacts from the Bronze Epoch in alluvial sediments in Bulgaria (Z. Tsintsov)

Investigation is performed on the distribution and typifying of gold artifacts from the Bronze Epoch that are found in alluvial sediments on Bulgarian territory. Until now, such objects have been found in sediments of the following rivers: Struma, Ogosta, Iskar, Palakariya, Djerman, Dragovishtitsa, Uineshtitsa, Topolnitsa, Medovska, Dulgidel Ogosta, Zlatitsa, Luda Yana, Arda, Maritsa, and many of their tributaries. A general regularity in the distribution of these gold artifacts in the depositions studied is that almost everywhere they have been observed, we found traces of ancient gold mining. As a whole, the objects are very small and the majority of them fall in the grain fraction from 1 to 5 mm, the biggest ones reaching a length up to 25 mm. According to their construction features the objects can be subdivided into simple and complex. The simple alluvial gold artifacts are represented mainly by: beads, lamellas and wires, balls, etc. The complex artifacts are applications and parts of finery. The widespread distribution of the discussed artifacts in the alluvial sediments of Bulgaria indicates that the mining and processing of gold on the Bulgarian territory during the Bronze Epoch has already been a quite widely distributed human activity [62, 154].

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17. Composition of a stone tobacco pipe from the Regional Historical Museum of the town of Kyustendil, Western Bulgaria (R. Stoyanova, O. Vitov, I. Marinova)

First data on the composition of a stone tobacco pipe from the archaeological reserve “Pautalia-Velbuzhd-Kyustendil” are presented [54, 148]. It has been found in a cultural layer dated from the Ottoman period during a rescue excavation in the town of Kyustendil and has no analogues so far among the museum exhibits in Bulgaria. The studied stone tobacco pipe is made of a massive homogenous microcrystalline dark green rock with a greasy luster (Fig. 1), with its outer surface polished. The pipe is 6.7 cm in length and 4.6 cm in height with a bowl and a stem united at an angle of 66°. The X-ray diffraction pattern of a powder sample from the stone tobacco pipe is consistent with chlorite. Quartz was observed using a binocular microscope. Thus, the studied rock is determined as a quartz-chlorite stone. The chlorite is iron-magnesian one with close FeO and MgO contents, but with predominance of the latter. It is ferrous clinochlore (ripidolite and pycnochlorite according to the nomenclature of Hey, 1954). The approximate temperature of the chlorite formation, as estimated after the compositional chlorite geothermometer of Cathelineau (1988), ranges from 289 to 353°C and indicates green-schist facies of metamorphism or hydrothermal-metasomatic process. Possible source rocks for producing the pipe are either a massive layer of chlorite phyllites and schists or chlorite rocks formed during alteration of ultramafic rocks from Bulgaria or chloritites originating from hydrothermal alteration of volcanic rocks outside Bulgaria. If it turns out that the studied tobacco pipe is unique for Bulgaria, most probable is the latter origin of it – production out of Bulgaria and then import in this country.

Fig. 1. View on the studied stone tobacco pipe from various points

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18. Petrography and geological setting of a prehistoric rock-hewn sanctuary in the Eastern Rhodope Mountain, SE Bulgaria (I. Marinova, P. Nenova)

Vaulted niches, rock graves, and rock discs hewn into the base of a vertical rock wall were discovered in 1997 to the south of the village of Raven, Momchilgrad District, Eastern Rhodope Mt, SE Bulgaria [35, 125]. These rock-hewn features are identical in shape and manner of working with such from the Momchilgrad District suggested as Thracian rock-hewn sanctuaries. The petrography of the rocks, into which the sanctuary is hewn, is described – they are tough, lightweight, soft and porous massive red-brown vitric-crystal lapilli rhyolitic tuffs of the Third Felsic Volcanism manifested in the Momchilgrad Depression (Sixth Oligocene Horizon; Raven Volcanic Complex) of Middle Oligocene age. The tuffs consist of crystal clasts (about 30 vol.%), vitric clasts (about 20–30 vol.%), lithic clasts (below 1 vol.%) and a matrix (around 40–50 vol.%). The crystal clasts are represented by quartz, oligoclase, potassium feldspar, biotite, adularia, zircon, and ore minerals. The vitric clasts consist of pumiceous and compact volcanic glass. They are not flattened and pale coloured, thus lending a variegated outlook on the rhyolitic tuffs. The lithic clasts of rhyolite are met rarely. The matrix of tuffs is red-brown in color due to iron oxides and hydroxides and consists of poorly-welded ash glassy pyroclastics of amygdaloidal texture. Zeolite (clinoptilolite) and opal-C or opal-CT have been formed during the alteration of volcanic glass. The zeolitization is 25–50 vol.% as the pumiceous vitric clasts are entirely zeolitized. Clinoptilolite contains K and Na according to most electron microprobe analyses, the content of K being higher than that of Na; the Ca-containing compositions with Ca ³ K+Na were also determined. In the vitric clasts and the matrix clinoptilolite is microcrystalline (sized up to 5–10 mm) but in amygdales it forms platy crystals between 5–10 and 200–300 mm long and between 1–2 and 50–70 mm thick. The paper provides also X-ray diffraction data on clinoptilolite. All amygdales are encrusted with fan-like clinoptilolite aggregates and with parallel fibrous aggregates of positive elongation, probably of cristobalite, reaching up to 100 mm in length.

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19. Petrographic study on artifacts from a temple of Sabazios in the village of Porominovo, Kyustendil district, Western Bulgaria (O. Vitov, P. Nenova)

Stone artifacts from a temple of Sabazios, dated to 2–3 century AC by inscriptions, were uncovered during excavation in “Zlatkova vodenica”, the village of Porominovo, Kyustendil district [43, 136]. The petrographic study carried out on stone fragments from this temple showed that blocks of coarse-grained, fine-grained and hydrothermally altered granites originating from the slopes of western Rila mountain in the water-catch-basin of Rilska river, had been used as a material for its building. Such granites are unsuitable for quarry production and construction due to tectonic impact and weathering. The conclusion is that the stone fragments from the Sabazios temple are built up of granite blocks from fluvial-glacial sediments (boulders) in the Kyustendil region and that there are no arguments to suppose a quarry production thereabouts. The presence of travertine is indicative of nearness of the Sabazios temple to the excavation in the village of Porominovo.

Fig. 1. A granite pedestal dedicated to Sabazios from archeological excavation near the village of Porominovo, Kyustendil district (left), a petrographic specimen of it (right upper) and microscopic pictures (right bottom).

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20. Studying the distribution of stone riverside knolls (mounds from gold production) in Kyustendil district after topographic maps scaled 1:126 000 (O. Vitov)

A comparison is made between the distribution of gold in the Kyustendil district based on data from stream-sediment surveys carried out in the period 1950– 2000 (a total of 8494 stream-sediment pan-concentrated samples, 1346 of them containing gold) and the distribution of 344 stone riverside knolls put on old topographical maps emitted in the period 1878–1923 [98]. It was calculated that about 30 kg gold in the period 1878–1923 had been produced from the rivers in Kyustendil district, while about 300 kg was expected for the period of Ottoman domination before 1878. It was obtained that the probability for discovering gold close to a stone riverside knoll is smaller than the expected one, which means a reduction of the halos of mechanical dispersion of gold due to gold production, and that the stone riverside knolls are in fact heaps from gold production. Data on using stone riverside knolls as construction material in the Antiquity and the Medieval are presented. The method for studying stone clasts of river sediments is briefly described. The data are processed using a specially created computer program (QBASIC for WINDOWS-98) for comparison of data of the type “point” with such of the type “relief” (probability map for discovering gold).

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4.4 Modeling and modification of mineral systems

21. Phase transformations in dc-electrochemically treated natural basalt (I. Mouchovski, M. Tarassov)

Obtaining reliable data on electrical properties of basalts in a large temperature range around the solid-liquid phase transition is important for studying the structural modifications caused by compositional variations and changes in some external parameters such as temperature, pressure, and environment. This, on its turn,one may search for controllable structural alterations in order to propose new applications of this composite silicate material. The electrical conductivity σ seems to be the intrinsic parameter most sensitive to even insignificant T-variations and to possible phase transformations and alterations in the transport and structural properties. Thus, the dependence of σ on temperature has to be cautiously interpreted accounting for all the external effects due to the experimental specificity of the measurement technique used [90].

The study aims at analyzing the temperature dependence of electrical conductance for dry basaltic samples in ambient (oxygen fugacity of 0.2 bar). The object is tholeitic basalt from Bukovo district (Bulgaria), silica and titanium poor (SiO2 » 42 wt%, TiO2 » 2.6 wt.%), iron- and aluminum-bearing (13 wt.% total Feamount, Al/(Al+Si) » 0.222), as Fe3+/(Fe2++Fe3+) » 0.4 indicates moderate oxidizing conditions of solidification. Randomly chosen basalt fragments are fused, quenched, and grounded several times in air so that to provide a homogeneous starting powder material with a Fe3+/(Fe2++Fe3+) ratio reaching up to 0.94. A parallelepiped-shaped corundum cell supplied by two fixed in parallel platinum- plate electrodes is loaded by powder basaltic material and used for monitoring the up-down T-cycles (an amplitude of 3–5 K) and the electrical resistance, R, by an intelligent multi-meter Thurlby-1905 allowing data-storage with a period of 0.333–104 s. The loaded cell was not taken out of the furnace during runs that guarantees invariant thermal-field conditions. The reproducibility of the obtained data during T-cycling is fairly good under similar experimental conditions. The cell construction ensures a maximum surface exposure to ambient furnace atmosphere, while the possible basalt- corundum physical-chemical reactions are restricted within a narrow zone nearby the cell bottom.

Unwanted polarization effects were investigated at different external voltages applied in a large range of temperatures, and the corresponding corrections were then plotted as a log (R–1) vs. 1/T dependence. The high-temperature limit was 1345°C, thus restricting the influence of the thermal ionization of some network forming oxides, while temperatures below 560°C were not considered as a significant temperature leakage conductance appeared in the sample assembly at lower T. By analyzing directly the obtained R–1-data, we excluded the influence of the cell-factor, assuming it retains fixed during the runs. Such an approach is especially useful when experimental conditions such as the frequency of heating/cooling cycles and its changing (continuously or step-wisely) are being varied in broad limits. As seen in Fig. 1a, none of the curves in the heating periods is following an Arrhenius’ linear trend even within the relatively narrow temperature range out of the solid-to-liquid transition region. Instead, the curves show several discontinuities that appear at different points forming sections with from slightly to significantly altering slopes. Such behaviour indicates that the fused solid sample contains probably some amount of re-crystallized mineral phases appearing during the cooling cycle of the preceding run. Nevertheless, the liquidus temperature may be specified to be between 1206 and 1254°C, while the solidus one appears at about 1093°C, thus outlining a region for solid-liquid transformation of 100–150 K. The lowest curve, marked by empty circles, is thought to manifest a significant amount of crystal phases, as it indicates a very fast decrease in the transition region, becoming rapidly one and a half order of magnitude lower than for the highest curves, where a glassy state is supposed to dominate. The observed divergences result from the different conductive mechanisms in the molten, glassy, and crystal phases that may interfere with each other in the transition region, where partially molten material is proved to wet the boundaries of crystal grains/edges, as well as in the solid state T-region where the intrinsic ionic conduction in disorderly disposed silicate structural units (glassy state) does not correspond to point defects conduction (migration of electron holes) in crystal phase.

Fig.1. Logarithmic temperature dependence of electrical conductance at up-down T-cycling. a. Heating portions at several different T-regimes containing sections of continuous rise by rate of 30–600 K/h or stepwise rise with some T-dwells. b. Cooling portions performed either controllably(30–600 K/k) or/and by uncontrollable quenching the sample. 1 – initial data fitting; 2 – fitting after correction for polarization effects.

Considerable divergences for heating portions’ curves, reflecting in high scattering of R–1-data in 1/T-space, are in contrast with the data corresponding to cooling portions’ curves that outline a single log (R–1) vs. 1/T dependence varying within ± 0.1 log units (Fig. 1b). Such result suggests that all crystal phases, produced eventually during a preceding relatively slow cooling, have been molten at any heating up to 1345°C except, probably, to some small amount of high-temperature min-eral phases, whose influence on bulk conductivity could be only of second order. Here, the discontinuity at » 1017°C marks the upper bound for solid state T-region wherein the slope remains nearly constant down to 610°C, revealing a dominance of ionic conductivity with activation energy of approximately 0.4 eV. This value is » 57% of that (0.7 eV), reported in literature for basaltic melts of similar composition, which indicates easiness for conductive metal cations under the particularly chosen run conditions used. More likely, the reason for the established lower activation energy lies in the shift of polarization-depolarization equilibrium to direction of higher abundance of silicate structural units with a higher content of non-bridging oxygen.

Backgrounds for such a suggestion are both the oxidized ambient that supplies a high buffer of O2– anions near the cathode and relatively high content of ferric ions acting as both, network modifiers and network formers. In conclusion, the electrical conductivity, the kinetics of ionic and/or other types of transport phenomena can be studied and interpreted in term of melt structure put under controlled experimental conditions. Besides, conductivity measurements performed with a very high precision appear potentially sensitive to any physical-chemical changes in the melt and glassy, including polymerization-depolymerization equilibriums and high order phase transformations.

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22. Changes in the phosphorite composition and properties during mechanical activation (K. Tõnsuaadu, T. Kaljuvee, V. Petkova, R. Traksmaa, K. Kirsimäe)

Mechanical activation can be characterized as an ecologically clean method for increasing reactivity of minerals not needing any chemicals and not producing wastes. Mechanically activated phosphorites and apatites are proposed for use as fertilizers either directly or in complex fertilizers. The impact of mechanical activa-tion on the reactivity of apatites is based not only on the decrease of the particle size but can also be related by changes in crystal structure. Less attention is paid on the possible changes in the chemical composition of phosphorites upon mechanical treatment in a planetary mill. The chemical and mineralogical composition of phosphorite concentrates from Tunis, Estonia (Kabala and Toolse deposits), Uzbekistan (Dzheroi-Sardara), and Kazakhstan (Dzhanatas) were studied before and after mechanical activation in a planetary mill for from 5 to 240 minutes. It was found that the solubility of phosphorus in citric acid solution increases with the duration of treatment (Fig. 1).

At the same time, the specific surface area of the activated samples increases during the first 10–30 min and decreases afterwards (Fig. 2). The observed changes in the characteristics of the phosphorite concentrates depend on their mineralogical composition.

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23. Investigation of Zn sorption by natural clinoptilolite and mordenite (N. Lihareva, L. Dimova, O. Petrov, Y. Tzvetanova)

Natural zeolites clinoptilolite and mordenite are potential adsorbent agents for metal cations because of their porous structure, high specific surface and cation exchange capacity. Their application as sorbents is important for purification of wastewater or for metal immobilization in the processes of removal of heavy metals from polluted soils. Agricultural application of natural zeolites includes also their use as fertilizer, when metals, adsorbed on zeolites are released under control in order to compensate for nutrient deficiency in microelements of some soils or as soil-additives to modify its water regime, physical properties, pH, etc.

In this work clinoptilolite and mordenite rich rocks were evaluated as inorganic Zn releasing carrier promising for use in agriculture. The chemical composition of the two samples was determined by AAS, inductively coupled plasma atomic emission spectrometry ICP-AES and gravimetrically (silicon). Powder XRD analysis was used to determine the mineral composition of the initial zeolite samples. An 80 and 75 wt.% of clinoptilolite and mordenite contents were determined, correspondingly [87].

The potential for sorption of zinc by both zeolites was evaluated by studying the sorption isotherms. Langmuir and Freundlich equations were applied to describe the sorption equilibrium of the used zeolites. The Langmuir model used is:

The Freundlich model used is:

The calculated parameters according to Langmuir and Freundlich adsorption equations are presented in Table 1.

Table 1. Langmuir and Freundlich equations and model parameters for sorption of Zn on clinoptilolite and mordenite

Table 2. Amount of sorbed zinc and EDTA extracted zinc

Zn sorption is in the order clinoptillolite > mordenite.
For prediction and assessment of mobility of sorbed zinc, we used in our study EDTA according to the method proposed by Ure et al. The results are presented in Table 2.

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24. Zn-exchanged clinoptilolite – a powder XRD study of the structural changes (L. Dimova, G. Kirov, O. Petrov, N. Lihareva)

Ion exchange properties of clinoptilolite are utilized in practice and the study of these processes is progressing. Clinoptilolite displays selectivity towards the metals of the first and second group as well as for Al³⁺, Fe²⁺, and NH₄⁺, in the following selectivity decreasing order: Rb⁺, K⁺, NH₄⁺, Ba⁺, Sr²⁺, Na⁺, Ca²⁺, Fe²⁺, Al³⁺, Mg²⁺, Li⁺. Big monovalent cations like Cs are preferred by the microporous structure of zeolites but for small bi-valent cations the selectivity is low. For Cd, Cu, and Zn it is in the order Cd²⁺>Cu²⁺>Zn²⁺.The antibacterial properties of zinc are used in cosmetics and medicine in various preparations for local therapy of skin deceases caused by Propionibacterium acnes or injuries. The system erythromycin – zinc is more effective when during the contact with skin the useful components are released gradually. Clinoptilolite is a suitable material for such an effect as it ensures gradual release of zinc in a medium of erythromycin.

The purpose of the present paper is to study the structural changes that take place in clinoptilolite, when undergoing greater Zn²⁺ exchange at higher temperatures and durations [9, 105]. Fractions of clinoptilolite rock sample were enriched in clinoptilolite by separation with heavy liquid. Zn2+ exchanged form was obtained by placing clinoptilolite material in teflon-lined autoclaves with 1M solution of ZnCl₂ at 100°C for 6 days duration. The solution was renewed on two days intervals sampling material for analyses. After the 6-th day the samples were decanted, washed with distilled water, and dried at room temperature. The powder XRD experiments were done in the range 8–50° 2q (DRON 3M, Fe-filtered CoKα radiation). The chemical analyses were done with AAS for the Zn exchanged modifications and with wet chemical analysis of the light fractions after separation.

Table 1. Content of Zn (wt.%) after ion exchange determined by AAS in different clinoptilolite fractions

The light fraction of the clinoptilolite sample is evidenced by XRD phase analysis to contain mainly clinoptilolite and always traces of opal-C, which is difficult to be removed. There are obvious intensity changes of reflections in the clinoptilolite XRD pattern after significant Zn2+ exchange (Fig. 1). It is seen from the figure that when comparing the diffraction patterns of the initial and the exchanged samples there are apparent changes in some of the peaks. Namely, slight lowering of I020 and more expressed lowering of I200. Also, the peaks 201 and 111 decrease in intensity with the exchange while peaks 001 and 311 increase in intensity. Interestingly, the small peak 220 fully disappears even at the 2nd day of Zn exchange. The shown intensity changes in the powder XRD patterns of Zn exchanged clinoptilolite are undoubtedly due to changes in the cationic sub-lattice in the structure of this zeolite. Additionally, the refinement of the unit cell parameters showed constant increase of the values with the content of exchanged Zn. For the initial clinoptilolite sample we have obtained a = 17.694 Å, b = 18.045 Å, c = 7.408 Å, β = 116.28°, and V=2120 ų, while the exchanged for 30 days sample has the following parameters: a = 17.709 Å; b = 18.114 Å; c = 7.412 Å; β = 116.09°; and V=2135 ų (0.7% increase). AAS confirms the XRD data for Zn content in clinoptilolite after ion exchange (Table 1). From the theoretically possible 7.1% Zn²⁺ ions for the studied clinoptilolite (K1.8Ca1.7Na0.5Mg.0.2)6.1Al5.8Fe0.22 Si29.94O72´20H2O) we have reached exchange level of 6.8%. Best exchanged is fraction 0.032–0.016 mm (sample C2). Possible explanation for these results is that this fraction contains less opal-C than C3 (higher clinoptilolite content) and it is finer than C1 (greater exchange surface).

The performed studies reveal some crystal chemical peculiarities of Zn-exchanged sedimentary clinoptilolite, which are needed background for future more detailed structural investigations to explain the localization of Zn2+ ions in the channels of clinoptilolite and predict the possible desorption processes connected with biological contacts.

Fig. 1. Powder XRD patterns of clinoptilolite sample (fraction 0.032–0.016 mm) from Beli plast deposit (initial) and its Zn2+ exchanged forms for duration of 2, 4, and 6 days.

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4.5 Synthesis, composition, structure, and properties of minerals and new materials

25. Reliability of optical transmission measurements for studying simultaneously grown Ca1-xSrxF2 single crystals of varying composition (I. Mouchovski)

Calcium strontium fluoride crystals are promising for easily compensating the spatial-dispersion-induced birefringence effect that appears as a key problem in micrometer-lithographic optical systems. Such mixed fluoride crystals have already been grown using an optimised Bridgman-Stockbarger technology (Ann Rep 2006). The further improvement of optical quality depends on its efficient controlling by precise measurements of some characteristic parameters like the external optical transmittance, t, determining the absorption and light-scattering losses that is a convenient parameter for relating the crystal quality with the conditions of growth (see Ann Rep 2007). To measure t in the vacuum ultra violet (VUV) spectral range one needs a highly sensitive VUV-spectra-photometer, while in the UV to IR ranges may use either a high sensitive UV-spectra-photometer or laser inspection of optically finished samples. Here we present results from a comparative analysis of the summed absorption and light-scattering losses per unit optical path, Labs+sc/lwin, and their alteration, Labs+sc/h2-1, along the length of a series of Ca1-xSrxF2 ingots with varying calcium-to-strontium ratio, grown simultaneously in a multi-camera crucible with axi-symmetric bowels [85, 86, 113]. The aims are: 1) to obtain reliable empirical relationships between quality-determining parameters and the shift of the position of the front of crystallization (CF) along the furnace temperature field; 2) to verify the suitability of the obtained relationships for efficiently controlling the simultaneous growth of calcium strontium fluoride crystals with significantly varying composition. We measured t by both spectral photometry (SPh) and vapour-laser irradiation (VLIr) technique for two series of windows, specified according to their position along the ingot, namely ser. 1 for “lower” positioned and ser. 2 – for “upper” positioned about 12 mm apart. The optical transmission spectrum is measured in the UV – near IR range (190–900 nm) using a highly sensitive spectrophotometer, Varian Cary 100, the values of t at 248.6, 510.6 and 900 nm being used for comparison with the corresponding values measured at 248.6, 510.6 nm, and 6450 nm by the VLIr technique. The optical parameters introduced in that way are related by

with l_win being the window thickness, h2–1 the distance between lower and upper windows, while the refractive index, nmix, is calculated depending on mixed crystal composition by nmix = (1–x)nCaF2 + xnSrF2. The method of Quenched Interface (QI) determination in a fixed crucible is applied for deriving empirical formulas for the CF-shift in a particular bowel to set up the thermal conditions and the composition of mixtures. Two growths (Nos. 1 and 2) were run out, differing in their temperature regimes in the furnace zones and in the speed of crucible movement. The performed investigation manifest (Fig. 1): first, both techniques provision a reliable qualitative analysis for recording and interpretation of any alterations in absorption and light-scattering losses per unit optical path, depending on the wavelength, composition of grown boules, and growing conditions; second, it exists some structural inhomogeneous areas in testified samples, revealing themselves with rising up the scattering probability when ë becomes longer. The SPh manifests impressively strong correlations within studied UV–NIR range that verifies the high reliability of this technique. At the same time, the VLIr leads to lower values for correlation coefficient R in comparison with those obtained by SpPh, as R decreases towards IR due to disordering of data points and rising up of their SD. More likely, the reason for such behavior lies in relatively large spot of laser beam, different in size for the used vapor lasers, which should promote an increasing effect of any structural inhomogeneity on total attenuation for passing beam. Longitudinal inhomogeneity of grown boules is assessed following the variations of Labs+sc/h2–1 on strontium content x and λ within UV–MIR (Fig. 2). Since CFshift should also depend on x, this way it is found out an indirect relationship between

Fig. 1. Linear regression fit for two series of the absorption plus internal light-scattering losses in Ca1-xSrxF2 optical windows obtained by VLIr (x) and by SPh (xx) at: 1 – 248.6 nm (R = 0.9825, SD = 0.42); 2 – 510.6 nm (R = 0.7766, SD = 0.0524), 3 – 900 nm/6.45 μm (R = 0.7287, SD = 0.3685).

Fig. 2. Difference in the absorption plus light-scattering losses between pairs of optical windows prepared from non- adjacent parallel sections of Ca1-xSrxF2 boules as a function of strontium content x at 248.6 nm (o); 510.6 nm (·) and 900 nm/6.45 μm (r).

Fig. 3. Reduced positions of the CF and the conical crucible’s unit during the growing of Ca1- xSrxF2 crystals: run 2: (·) – 0.383, (r) – 0.408, (q) – 0.436, (r) – 0.471, (n) – 0.509, (¯) – 0.554, (u) – 0.608, (v) – 0.675, (o) – xcon*.

structural and growing parameters. It is seen a larger absolute divergence from zero for run 1-boules compared to run 2-bouls. The differences for run 1 are positive with exception of one boule (with the lowest x of 0.0073), whereas they appear negative or near to zero for run 2-boules. Mostly run 1-boules show higher divergences into the VIS compared to UV and IR regions that is just the opposite to run 2-boules, the Labs+sc/h2–1-values of which approach zero in VIS. The established trend for enlarging the parameter Labs+sc/h2–1 towards the top section of the run 1- boules testifies for changing to worse growing conditions during crystallization. At the same time, the growing conditions during crystallization of run 2-boules turn out either constant (for three of the boules) or change to better (for the rest five ones) that corresponds to the observed variations of Labs+sc/h2–1-values nearby or noticeably below zero. For two boules (with x » 0.38 and » 0.5) the divergences appear insignificant approaching closely zero, which manifests structural homogeneity along boules’ height, and suggests for reaching the optimum in growing conditions. The optical quality of grown boules, assessed by involved semi-empirical parameters, is related to growing conditions via the shift of CF-positions, xCF (Fig. 3).The growing conditions for run 2 appear much more favourable to provision a normal growth in all crucible compartments at steeper vertical temperature gradient and gradually changing negligible shift for mostly CFs positioned almost entirely within relatively large adiabatic furnace zone, which is precondition for perfect crystal quality.

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26. Synthesis and characterization of Zn-containing calcium phosphates (D. Rabadjieva, R. Titorenkova, O. Petrov, R. Gergulova, R. Ilieva, E. Dyulgerova, Ch. Balarew, L. Konstantinov)

Calcium phosphate-based ceramics are prospective materials for bone reconstruction and remodeling. At the same time, zinc has a stimulatory effect on the bone formation and an inhibitory effect on bone resorption, which is the reason for  using Zn additives to prepare materials that promote tissues self-regeneration instead of their replacement. The modern biomimetic methods for preparing such materials are associated with synthesis of calcium phosphates in simulated body fluids (SBF).
Zn – substituted amorphous calcium phosphates (ACP) are prepared through wet precipitation of calcium chloride and zinc chloride with potassium hydrogen phosphate in a modified SBF. The precipitates are then treated in a conventional SBF at a temperature 37°C for different periods of time. The transformation of the amorphous phases into nanometer-sized apatite upon SBF treatment is studied by chemical analysis, XRD and FTIR spectroscopy. The increase in the Zn concentration leads to a significant delay of the rate of crystallization and to a change in the chemical composition of the solid phases [94].
In another experiment, the precipitates are sintered at a temperature of 800°C and atmospheric pressure, leading to the formation of whitlockite (β-TCP) as the main phase in the composite. The isomorphic substitution of Zn2+ for Ca2+ in the structure of β-TCP is performed in a stepwise manner and results in a linear decrease in the unit cell parameters and volume with increasing the concentration of Zn. The results obtained indicate that the addition of Zn promotes the formation of single-phase β-TCP ceramics [82].

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27. Mechanochemical synthesis of layered double hydroxides (Z. Cherkezova- Zheleva, D. Paneva, E. Manova, B. Kunev, V. Petkova, I. Mitov)

The exact conditions for preparing layered double hydroxides by mechanochemical activation were investigated and parameters such as the number of grinding balls, the weights of precursors, duration of milling, etc. are specified. Both the synthesised samples and the precursors were tested by X-ray diffraction, Mössbauer spectroscopy and DTA/TG analysis in order to specify their chemical and phase composition, dispersity and thermal decomposition temperatures. The obtained data shows that the mechanochemical treatment of the initial compounds Mg(OH)2 and FeCl3 results in the synthesis of the studied LDH compound – ironmagnesium hydroxide chloride. The thermal treatment of this compound leads to formation of iron-containing products and magnesium-containing oxide phases [7, 103].

Fig. 1. TG-DTA-DTG curves of Iron-Magnesium Hydroxide Cloride.

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28. Novel nanostructured materials accelerating osteogenesis (B. Trajkovski, J. Karadjov, B. Shivachev, A. Dimitrova, S. Stavrev, M. Apostolova)

Osteoporosis is a disease in which the mineral density of bone is reduced, its micro-architecture disrupted, and the expression profile of non-collagenous proteins altered. Normal fracture treatment is a complicated, multistage process, affected by cells evidence and regulated by local and systematic factors. The objective of the study was to develop new bioactive nanostructured materials, in both acellular and autologus cell-seeded forms to enhance bone fracture fixation and healing thought creating highly porous structures which will promote osteogenesis. The approach to develop highly effective hydrogels for counteracting the effects of osteoporosis followed different ways (a) synthetic and biological polymer chemistry with nanotubes and (PNT) (b) experiments with EPC cell models. The results showed that in vitro EPC transformation to osteoblasts was enhanced in the presence of PNT. This results suggest that synthetic polymer-nanocomposite materials may exhibit certain properties that are comparable to natural one, and nano architecture may serve as a scaffold for promotion of EPC differentiation and biomineralization [97].

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29. Crystal chemical characterization and thermal behavior of new synthetic water containing zirconosilicates (R. Nikolova, K. Fujiwara, N. Nakayama, V. Kostov-Kytin)

A new zirconosilicate of chemical formula Na2Zr7Si2.5O20.3H2O and its K and Ba ion–exchanged forms are characterized by means of X-ray diffraction, TG-DTA and HRTEM analyses [91]. Preliminary information about space group and unit cell parameters of the studied compound is reported. The analyses of the ED patterns confirm only two of the lattice parameters and indicate C centred monoclinic cell and doubled b-parameter. If we calculate the c-lattice parameter as a function of the first XRD peak position we have two possible unite cells a = 11.05, b = 6.4, c = 11.57 Å, β = 92° (C2,Cm,C2/m) and a = 11.05, b = 6.4, c = 23.14 Å, β = 92° (Cc, C2/c). The Le Bail extraction and whole profile structureless fit resulted in Rp 14.37% Rw 21.61% for C2/c a = 11.18, b=6.39, c = 23.08 Å, β = 90.72°. The structural peculiarities of the studied compound are compared with those of other earlier reported zirconium compounds, with similar powder diffraction patterns and unknown crystal structures. An arrangement of the zirconium polyhedra within the crystal structure of these materials is proposed with a view of the Zr4+ radius size and the related with it impossibility for this cation to constitute their frameworks as edge-sharing octahedra.

Fig. 1. HR image and SAED pattern obtained from a crystallite oriented parallel to the sample surface.

The crystal structure of a new small-pore framework sodium zirconosilicate monohydrate Na2ZrSi2O7·H2O is determined by powder structure refinement [92]. The studied compound crystallizes in monoclinic system with space group C2/c, a = 5.4715(4); b = 9.4111(6); c = 13.0969(8) Å, β = 92.851(7)°. Its framework consists of layers built of ZrO6 octahedra and SiO4 tetrahedra and forming condensed [Si2O7] pyrogroups by connection. The sodium ions and water molecules are placed in channels set up between the layers. The stoichiometric and structural similarity of the studied phase with eight waterless compounds having general chemical formula A2(3)MT2O7 (A=Na,K; M=Zr,Lu,Sc; T=Si,Ge) has been established [137]. The topological relationship of their structures is interpreted in the light of spatial combination of silicon and zirconium polyhedra as basic building units into larger composite building units and their three-dimensional arrangement. It is pointed out that the title compound is the only water containing material from the studied series. The degree of the framework deformation of the considered compounds is evaluated using the pyrogroup configuration and the framework density (FD) parameter, thus contributing to better understanding the crystal chemistry of zirconosilicates and their analogs. The sensitivity of the studied framework topology to tiny variations in the reaction medium and precursor chemistry is indicative that the preparation of MT framework compounds with tailored pore system depends on the appropriate choice of physicochemical conditions.

Fig. 2. Crystal structure of Na2ZrSi2O7·H2O: a) MT layer; b) 3D structure of framework; distances between oxygen atoms are given to illustrates channel width; c) Na ions and water molecules.

Fig. 3. Schematic presentation of the temperature-induced phase transformation.

The small pore Na2ZrSi2O7.H2O undergoes two phase transformations upon heating [30, 118]. The first low-temperature one connected with the dehydration process passes without energetic changes and converts the monoclinic Na2ZrSi2O7·H2O into the orthorhombic Na2ZrSi2O7. The process is reversible as evidenced by the rehydration of Na2ZrSi2O7 heated to 300°C. The second high-temperature transformation is a typical reconstructive transition causing transformation of [M2T6] into [M2T4] that results in the formation of a compound analogous to the mineral parakeldyshite. Unlike the first transformation the second one is irreversible and does not allow hydration of the compound.

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30. TiO₂/ZnS nanocompozites – characterization and visible-light photocatalytic activity (V. Stengl, S. Bakardjieva, V. Houskova, N. Petrova, Yu. Kalvachev)

TiO2 and ZnS have widely been used in environmental catalysis. However, they are photoactive in the near UV spectral range and thus only 3–4% of the solar light is utilized. It is expected that the photocatalytic activity of the solitary TiO₂ would considerably be improved via the preparation of nanometer-scaled coupled semiconductors[53]. TiO₂/ZnS nanocomposites were prepared by the method of homogenous hydrolysis in aqueous solution with thioacetamide. The prepared samples were characterized by X-ray diffraction, high-resolution transmission microscopy, BET surface area analysis and porosity determination. The nanocomposites show an efficient visible-light photocatalytic activity to degrade the aqueous solution of Orange II dye, which is higher than that of commercially available TiO2 (Degussa P25), pure anatase TiO₂, or cubic ZnS nanoparticles. The composite sample with highest catalytic activity was obtained by hydrolysis of mixture solutions 0.63 M TiOSO₄ and 0.08 M ZnSO₄.7H₂O.

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31. Characterization of Mg-Al layered double hydroxides intercalated by squarate derivatives (N. Petrova, R. Petrova, R. Titorenkova)

Layered double hydroxides (LDHs) have received considerable attention as catalysts, ion-exchangers and organic-inorganic nanocomposites. The cationic layered framework allows a safe accommodation and a controlled delivery of biological molecules including various drugs. In the last years, the bioactivity of squaric acid and some of its derivatives as inhibitors has been reported. Mg-Al LDHs containing squarate (Sq) or hydrogensqurate (HSq) anions were synthesized and characterized by X-ray diffraction, IR-spectroscopy, DTATG and SEM [50]. The two anions into the LDH interlayer differ in their structural arrangement and symmetry. The DTA curves are typical of the LDH structure. All the effects observed in the DTA curves, related with dehydration, dehydroxylization and combustion of the organic species, maximize at a temperature higher for Sq-LDH (Fig. 1a) than for HSq-LDH (Fig. 1b) most probably due to a stronger hydrogen bonding of intercalation in the structure of the former compound. The SEM images of Sq-LDH and HSq-LDH samples (Fig. 2a and 2b) under a high magnification (15000x and 20000x, respectively) provide information on the crystallite morphology and size. These are either single platy hexagonally shaped crystallites of a diameter of 0.6–1.0 mm and a thickness of 0.06–0.08 mm or spheroidal twins of thin hexagonal plates forming sponge-like aggregates.

Fig. 1. DTA and TG curves of the samples Sq-LDH (a) and HSq-LDH (b) in argon (solid line) and in air flow (dotted line).

Fig. 2. SEM images of Sq-LDH (a) and HSq-LDH (b). Scale bars: 1μm.

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32. Atomic rearrangement in Ca1-xSrxF2 crystals for x ~ 0.5 determined by XRD and TEM study (V. Dimov, B. Kostova, O. Petrov, L. Konstantinov)

In mixed two-cationic component systems, the chemical composition x affects the crystal structure, the transition between the two end phases (CaF₂ and SrF₂) not following a systematic pathway and passing through specific structural anomalies related to the formation of structurally incommensurate crystalline phases and inhomogeneous domains of one of the phases into the other [81, 85, 86]. Using XRD, HRTEM and SAED experiments and computer modelling, it is shown that during crystal growth the structure of Ca₁-xSr_xF₂ single crystals passes through the formation of non-homogeneously distributed domains of mixed Sr-Ca-F crystalline phases when the composition x changes between values below and above x = 0.5. We observed structural anomalies on both sides of this value, the structure of the mixed crystalline phases with x = 0.384 and x = 0.674 “adjusting” from a dominance of the CaF2 structure to dominance of that of SrF2. Thus, we show that one can specify the structure of such two-cationic crystals through comparing their experimental HRTEM and SAED images with such simulated numerically. Our experimental studies have shown that the isomorphic substitution of Sr for Ca and the structural changes resulting thereupon lead to the appearance of additional reflexes in SAEDI and to a change in the HRTEMI phase contrast, to a widening and/or splitting of the diffraction maximums characteristic of the presence of structurally defect multiphase systems, the studied crystals being built up of periodically distributed Ca and Sr-ions ordered in phases with x = 0.25, 0.5 and 0.75.

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33. Structure and change in anticonvulsant properties of 3-aminocycloheptanespiro- 5-hydantoin and 3-amino-cyclooctanespiro-5-hydantoin (P. Todorov, R. Petrova, E. Naydenova, B. Shivachev)

The crystal structures of 3-amino-cycloheptanespiro-4’-imidazolidine-2’,5’-dione  (I) {systematic name: 3-amino-1,3-diazaspiro[4.6]undecane-2,4-dione} and 3-amino- cyclooctanespiro-4’-imidazolidine-2’,5’-dione (II) {systematic name: 3-amino-1,3- diazaspiro[4.7]dodecane-2,4-dione}, have been determined [59]. In both compounds the polar hydantoin groups cause molecules to aggregate via N-H…O and N-H…N interactions. The cycloheptane and cyclooctane 3-amino-spiro-5-hydantoins exhibit crystal structure build of [011] layers based on hydrogen bonding of the polar hydantoin moieties, hiding them in the inner part of the plane, with non-polar, cycloalkane groups out in the open outer sides of the layers. Such manner of crystal packing is commonly observed for substituted spirohydatoindiones while the cyclohexane, cycloheptane, and cyclooctane non-amino spirohydantoindithiones show structures where the molecules are hydrogen bonded to build one dimensional chains only.

Comparison between structural results for reported compounds and unsubstituted hydantoins shows that the additional amino group and differences in hydrogen bonding pattern do not modify significantly the geometrical parameters of (I) and (II). In (I) and (II) the activation/deactivation of seizures is controlled by the hydantoin moiety, especially by the (N1) centre and the substituent present in position (N3), while the cycloalkane size influences only the degree of the induced activity.

Fig. 1. Hydrogen bonding sites and direction in (a) 3-aminocycloheptanespiro-4’-imidazolidine- 2’,5’-dione (IA) and (b) cycloheptanespiro-4’-imidazolidine-2’,5’-dione [8]; possible acceptors are denoted with red and donors with green arrows. Map colour coding of this figure indicates hydrophilic area with blue and hydrophobic space with white/grey.

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34. Excimer laser processing as a tool for photocatalytic design of sol– gel TiO₂ thin films (K. Starbova, V. Yordanova, D. Nihtianova, W. Hintz, J. Tomas, N. Starbov)

Nanostructured sol–gel TiO2 thin films spin coated on silicate glass plates are subjected to excimer (KrF*) pulsed laser irradiation in order to tailor their structure and photocatalytic properties. The surface morphology of virgin and laser-processed films are followed by applying electron optical imaging and atomic force microscopy. The evolution of the surface roughness and pore formation are shown to be accompanied by an shift of the optical absorption edge to the infrared wavelength range. Conventional X-ray diffraction analysis and high-resolution transmission electron (HRTEM) imaging are applied in order to obtain information on the phase composition. Co-existence of amorphous and anatase TiO2 phases in nonirradiated sol–gel films is found. It is established that after laser processing the most intense XRD anatase peak is shifted to lower 2θ values. The analysis of HRTEM images of film profiles evidences for the laser induced phase transitions. Formation of rutile and brookite TiO2 accompanied by evolution of oxygen deficient TinO2n-1 phases are identified in the subsurface region. The contribution of the laser processing for increasing the photocatalytic efficiency of laser-modified films towards oxidation of methylene blue water solution is demonstrated. The results obtained reveal a novel processingroute for designing sol–gel titania films with improved photocatalytical activity [52].

Fig. 1. High-resolution transmission electron micrograph of the subsurface region of a 300 nm thick TiO2 film after five-pulse irradiation. Ed = 300 mJ/cm2.

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4.6 Sixth Framework Programme of EU

35. Remote instrumentation in next generation grids (Yu. Kalvachev, V. Ganev, L. Macheva)

Within the RINGrid project, we carried out a systematic identification of the instruments and the corresponding user communities, the definition of their requirements as well as careful analysis of the remote instrumentation synergy with next generation high-speed communications networks and grid infrastructure [27, 108]. It was the basis for the definition of recommendations for designing next-generation Remote Instrumentation Services (RIS). White paper with the mean achievements was published (Fig. 1).

Evaluation of the synergy of remote instrumentation with next-generation highspeed communications networks and grid infrastructure will allow a better usage of the existing, often under-utilized research instrumentation, as well as network and grid infrastructure.
RIS creates new, previously unnoticed, possibilities for many research projects that would be impossible to perform because of the lack of specific, sophisticated research equipment. This is especially true for scientific communities from countries that cannot provide enough funds for their research infrastructure and for the required sophisticated equipment. The possibility of performing research through access to the grid-embedded remote instrumentation, with the utilization of nextgeneration high-speed networks, will even out their chances in the scientific world.
Even in the rich, developed countries, scientists are not always aware of the possibilities that remote instrumentation would offer in the near, predictable future. RIS put focus on the creation of new possibilities for remote-instrumentation-based cooperation among scientists from different countries, working in the same or closely related scientific domains.

Fig. 1. Overview of the White paper on remote instrumentation.

The most interesting conclusions, however, come from user observations that touch the sphere of Experiment Execution. It is apparent that all the existing platforms tried so far have some limitations in this respect. So there is a need for: Flexibility and adaptation to the user-specific experimental environment. This point touches the Experiment Execution Domain, and pertains to the capability of customizing a Remote Instrumentation platform involving a certain type of devices to perform a specific experiment.

Flexibility and adaptation of the user interface to the user’s skills and level of expertise. This is another requirement that stemmed from the user comments in our short experimentation phase. It would be highly desirable to have a Graphical User Interface capable of adapting to the level of user experience or to the needs of a particular experiment. Appropriate tools for self-training and learning-by-doing. The usage of remote instrumentation brings to a large extent a novelty in teaching experimental sciences through distance learning sessions. A topic to be investigated in the Experiment Execution Domain regards the development of tools by means of which users can perform supervised or even unsupervised training on the instruments, and gradually be acquainted with their usage.

All these capabilities should be embedded in business-value RIS. As a matter of fact, they are just a small instance of the flexible, user-friendly, workflow-oriented, orchestration services. We have attempted to provide the first set of elements for the conceptual design of a complete Remote Instrumentation Services Architecture [119, 142]. We pointed out what are, in our opinion, the most relevant aspects that should be the
subject of future study and development. The emphasis has initially been put on technological aspects, and on what is and will be shortly available in terms of middleware and networking technologies that may help in reaching the goals to be pursued in the RIS scenario. Then, the study has been complemented by using case analyses.

The main and absolutely necessary facilities identified are instrument virtualization, error monitoring and logging, accounting and monitoring/controlling of the experiment execution. Additionally, some other functional requirements exist: presence of selection services, availability of site functional tests, policy decision and enforcement mechanisms, input and output data management, and workflow man65 agement. Further (non-functional) requirements involve input management (in the preparatory phase), the presence of (and interaction with) local operator(s), and the presence of specialized visualization devices.

The non-strictly-technological comments by users suggest some additional requirements to be addressed mostly conceptually and algorithmically: flexibility and adaptation to the user-specific experimental environment, flexibility and adaptation of the user interface to the user’s skills and level of expertise, and appropriate tools for self-training and learning-by-doing. More detailed information can be found in project documents that specifically address the issues of technology-related and user-related requirements.

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5. International Cooperation

• “Remote instrumentation in Next-generation Grids (RINGrid)” – multilateral project, funded by the 6th Framework Programme of EC, and worked by CLMC in cooperation with: Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poland; Johanes Keppler University, Lintz, Austria; Greek
  Research and Technology Network S.A.; Technical University, Iash, Romania; Universidad Nacional Autonomia de Mexico; Cooperacion Latinnoamericana de Redez Avanzadas; Consorzio Nazionale Interuniversitario per le Telecomunicazioni, Parma, Italy; Consiglio Nazionale Delle Reserche (C.N.R), Rome, Italy; University of Surray, United Kingdom

• “Remote interactive tools for regional GRIDs of new generation” – joint research project between CLMC and the Technical University in Iasi, Romania, funded by the Bulgarian National Science Fund

• “Following the tracks of metallurgy of Ancient Thracia” – joint research project between CLMC and the National Institute of Archaeology and Museum – BAS (principle organization) and the University of Munster, Germany, funded by the Alexander von Humboldt Foundation

• “Synthesis of new inorganic ionites (titanosilicates and zirconium dioxide) and investigation of their efficiency for removing long-term radionuclides
  (as Cs, Sr) as well as toxic anions in waters and waste waters” – joint research project between CLMC and the Institute of Sorption and Problems of Endoecology, National Academy of Sciences of Ukraine, funded by the Bulgarian National Science Fund

• “Synthesis and crystal-chemical study of porous materials – potential catalysts, sorbents and biologically active materials” – joint research project between CLMC and the Institute of Inorganic Chemistry, Chezh Academy of Sciences, under the bilateral academic agreement with equivalent non-currency exchange

• “Preparation of organo-mineral composites for soil amendment” – joint research project between CLMC and the Tallinn Technical University and the Estonian Academy of Sciences, under the bilateral academic agreement with equivalent non-currency exchange

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6. Postdoctoral Fellows

• Dr. Rossitza Petrova – Department of Advanced Material Science and Engineering,
  Yamagouchi University, Tokiwadai, Ube, Japan

• Dr. Boris Shivachev – Department of Structural Biology, Scholl of Medicine,
  Pittsburgh University, USA

• Dr. Stanislav Ferdov – Department of Chemistry, University of Aveiro, Portugal

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7. PhD Scholarships

• PhD Student Milen Kadiyski – Laboratory of Chemical and Mineralogical Crystallography,
  University of Bern, Switzerland

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8. Visiting Scientists

• D.Sc. Stanislav Vassilev – National Expert of Bulgaria in the Joint Research
  Center of the European Commission, Institute for Energy, Petten site, The
  Netherlands

• Dr. Boriana Mihailova – visitor-professor on “Spectroscopy of minerals” and
  “Crystal Physics” at the Faculty of Earth Sciences, University of Hamburg,
  Germany

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9. Research Topics, announced for international partnership collaboration

Advanced multicomponent utilization of fly ashes from European coal-fired power stations
One of the environmental problems in Europe is the utilization of fly ashes (FAs) from coal-fired thermoelectric power stations (TPSs). This potential investigation will include characterization of various products recovered from FAs at European TPSs in an attempt for multicomponent FA utilization (MFAU). The MFAU is a necessary and unavoidable process due to the complex, heterogeneous and unique polycomponent composition of FA. The purpose will be: (i) to demonstrate how a low-cost waste can be transformed into useful, high-grade and valuable materials, which may find various applications; (ii) to provide a basis for the advanced, multicomponent, wasteless and environmentally friendly utilization of various FAs. The knowledge about the composition of FAs is sufficient to start an advanced and effective MFAU.

Structure and properties of new multifunctional materials
Synthesis and investigation of new materials of practical importance (nanosized zeolite-type natural and synthetic materials and thin films; ferric iron oxide materials; catalysts based on micro- and mesoporous carriers for removal of soot and nitrogen oxides from exhausted gasses; titanosilicate porous materials for ionexchange, sorbents, and catalytic systems; materials for optical and magnetic storage and processing of information; preparation and investigation of coal char based sorbents and catalysts). Characterization methods: X-ray diffraction, electron microscopy, Raman scattering and infrared absorption spectroscopies, optical measurements and chemical analysis. Education: M.Sc. and PhD in Mineralogy and Crystallography and Material Sciences.

Synthesis, structural characteristics and testing of crystal matrices for radionuclides immobilization
Synthesis of Synroc-like compositions seems to be an advanced alternative method of glass for long-term safety disposal of radioactive waste. In CLMC are synthesized Synroc-like specimens with different mineral compositions and variable mineral quantity of perovskite, hollandite, zirconolite, and hibonite. The research of stable matrices includes experiments to obtain Synroc materials with high unleachable qualities tested under extreme hydrothermal conditions, the behavior of which is highly resistant and environmentally convincing for public opinion. Methods:melt in electric furnace, inductive melting, sintering in solid state, sol-gel crystallization; Characterization: XRD, SEM, TEM, DTA/TG, IR; Testing: chemical analysis (AAS, ICP).

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10. Publications and Reports at Conferences and Local Meetings

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