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The copper-silver mineralisation Spremberg-Graustein in the Niederlausitz (Lower Lusatia) in SE Germany was explored in 1953–1974 resulting in the discovery of a Kupferschiefer type deposit with close to 100 million tons of copper ore at the stratigraphic base of the Lower Permian (Zechstein). This deposit contains 1.5 million tons of extractable metallic copper and considerable quantities of silver, lead and zinc. The deposit consists of the ore fields Spremberg and Graustein, which are separated by a graben structure.New mineralogical research using electron microprobe analysis has discovered a rich Cu-Se-Pb-Au-Ag-Bi-Ba mineralisation that previously was not known. The described mineral association occurs in the border area of the copper mineralisation and the haematitic Rote Fäule as well as within the Rote Fäule facies. This facies intersects the Zechstein base layers in the form of a wedge at a shallow angle crosscutting the geology. It causes lateral zoning of the deposit with several types of oxide and sulphide mineralisation.The principal selenide minerals are: clausthalite (PbSe) and klockmannite (CuSe) and subordinate eucairite (AgCuSe). Furthermore a significant occurrence of electrum (AuAg), native gold (Au), native silver (Ag), schapbachite (AgBiS2), and barite (BaSO4) belongs to the assemblage. In the deposit Spremberg-Graustein, near the border of as well as within the Rote Fäule facies , this assemblage is abundant. Mineralogical observations, microprobe analyses and phase relations are documented.Similar mineral assemblages are known from the copper-silver deposits of the Lubin-Sieroszowice-Rudna mining district in SW Poland . As mineralogical basis they contribute to the production of precious and strategic metals at the Polish KGHM Copper Mining Company. To date, in addition to the base metals, there already has been a considerable production of Au, Pt and Pd amongst others. These by-products improve the economics of those deposits considerably.The investigated mineralisation of the copper-silver deposit Spremberg-Graustein is of epigenetic nature and post-Variscan age. Various copper sulphides and mineral inclusions indicate a hydrothermal origin. It may represent a late phase of the multi-stage mineralisation in the deposit.

Boralsilite, the only natural anhydrous ternary B2O3-Al2O3-SiO2(BAS) phase, has been synthesized from BASH gels with Al/Si ratios of 8:1 and 4:1 but variable B2O3and H2O contents at 700-800 °C, 1-4 kbar, close to the conditions estimated for natural boralsilite (600-700 °C, 3-4 kbar). Rietveld refinement gives monoclinic symmetry, C2/m, a = 14.797(1), b = 5.5800(3), c = 15.095(2) Å, β = 91.750(4)°, and V = 1245.8(2) Å3. Boron replaces 14% of the Si at the Si site, and Si or Al replaces ca. 12% of the B at the tetrahedral B2 site. A relatively well-ordered boralsilite was also synthesized at 450 °C, 10 kbar with dumortierite and the OH analogue of jeremejevite. An orthorhombic phase (“boron-mullite”) synthesized at 750 °C, 2 kbar has mullite-like cell parameters a = 7.505(1), b = 7.640(2), c = 2.8330(4) Å, and V = 162.44(6) Å3. “Boron-mullite” also accompanied disordered boralsilite at 750-800 °C, 1-2 kbar.

Physical and chemical properties of four transparent, gem-quality musgravites from Sri Lanka are presented. These are the first data for samples of this rare mineral species originating from the numerous secondary deposits of this island. The musgravites were identified by Raman spectroscopy and electron microprobe analysis. Physical data such as refractive indices and densities are related with transition metal contents, especially with iron and zinc values. Mineral and multiphase inclusions indicate a formation of our samples in different environments. A musgravite crystal containing spinel exsolution lamellae is possibly formed in high grade metamorphic rocks, two samples with graphite and magnesite inclusions possibly originate from magnesian skarns.

Cubic AgBiS2 already known as synthetic compound for some time has been found at the Silberbrünnle mine near Gengenbach in the Central Black Forest. It is the first occurrence in nature. It forms inclusions in quartz and is associated with bismuth, acanthite, bismutite and pyromorphite. The grains of the mineral are anhedral and reach about 0.3 mm in size. They are sometimes partially altered and surrounded by the secondary minerals acanthite and bismutite. The colour is grayish black, streak black, opaque with metallic luster, hardness about 2 1/2, brittle, no cleavage observed. Density (calc.) 7.05 g/cm3. Reflectance values in air: 470 nm 45.19, 546 nm 44.73, 589 nm 44.32, 650 nm 43.94 %. Unit-cell dimension of the mineral a = 5.703 Å, Z = 2, space group Fm3m. Strongest lines of the powder pattern in Å: 3.290 (8) 111, 2.853 (10) 200, 2.014 (8) 220. Result of the chemical analysis (wt.%): Ag 21.83, Pb 18.10, Bi 42.39, S 16.15, total 98.47 %, yielding - on the basis of S = 2 - the empirical formula Ag0.80Pb 0.35 Bi0.81 S2 or simplified Ag(Bi, Pb)S2. This is close to the composition of a cubic phase synthesized by Hoda & Chang (1975) with 30.0 mole-% PbS, 33.8 mole-% Ag2 S and 36.2 mole-% Bi2 S3 and a unit-cell dimension a of 5.71 Å.

The crystal structure of a pale blue transparent Mn-rich fluorapatite (MnO: 9.79 wt%) with the optimized formula ∼(Ca8.56Mn2+1.41Fe2+0.01)P6O24F2.00and space group P63/m, a = 9.3429(3), c = 6.8110(2) Å, Z = 2 has been refined to R = 2.05% for 609 unique reflections (MoKα). The Mn in the Eibenstein an der Thaya, Austria apatite is strongly ordered at the Ca1 site: Ca1: Ca0.72(1)Mn0.28, Ca2:Ca0.96(1)Mn0.04. There is a linear variation in as a function of Mn content (r2= 1.00). The dominant band in the optical absorption spectrum of fluorapatite from Eibenstein is in the 640 nm region with E || c > E ⊥ c. The 640 nm band is attributed to Mn5+at the P site by analogy with previous studies. This interpretation is consistent with studies of well-characterized synthetic materials of the apatite structure that contain Mn5+. Because Mn5+has intense absorption in the visible region of the spectrum, if a small proportion of the total Mn is Mn5+at the P site, that substituent dominates the spectrum and the color of the mineral. To determine if the pale blue color is due to radiation effects, a fragment of the fluorapatite crystal was heated at 400° C for 1 hour, and the change in color was slight. All of these observations are consistent with the origin of color from Mn5+. Assuming that all the intensity of the 640 nm (E || c) absorption is from Mn5+, the concentration of Mn5+in this fluorapatite sample was calculated as 2.6% of the total manganese content (∼P5.96Mn5+0.04). The calibration was estimated from the spectrum of the related compound Sr5(P0.99Mn5+0.01)3Cl. The weak band at about 404 nm in the E || c spectrum may be the corresponding band for Mn2+in octahedral coordination.

The crystal structure of a pale blue transparent Mn-rich fluorapatite (MnO: 9.79 wt%) with the optimized formula ∼(Ca8.56Mn2+1.41Fe2+0.01)P6O24F2.00and space group P63/m, a = 9.3429(3), c = 6.8110(2) Å, Z = 2 has been refined to R = 2.05% for 609 unique reflections (MoKα). The Mn in the Eibenstein an der Thaya, Austria apatite is strongly ordered at the Ca1 site: Ca1: Ca0.72(1)Mn0.28, Ca2:Ca0.96(1)Mn0.04. There is a linear variation in as a function of Mn content (r2= 1.00). The dominant band in the optical absorption spectrum of fluorapatite from Eibenstein is in the 640 nm region with E || c > E ⊥ c. The 640 nm band is attributed to Mn5+at the P site by analogy with previous studies. This interpretation is consistent with studies of well-characterized synthetic materials of the apatite structure that contain Mn5+. Because Mn5+has intense absorption in the visible region of the spectrum, if a small proportion of the total Mn is Mn5+at the P site, that substituent dominates the spectrum and the color of the mineral. To determine if the pale blue color is due to radiation effects, a fragment of the fluorapatite crystal was heated at 400° C for 1 hour, and the change in color was slight. All of these observations are consistent with the origin of color from Mn5+. Assuming that all the intensity of the 640 nm (E || c) absorption is from Mn5+, the concentration of Mn5+in this fluorapatite sample was calculated as 2.6% of the total manganese content (∼P5.96Mn5+0.04). The calibration was estimated from the spectrum of the related compound Sr5(P0.99Mn5+0.01)3Cl. The weak band at about 404 nm in the E || c spectrum may be the corresponding band for Mn2+in octahedral coordination.

Reinvestigation of duhamelite, originally described as Cu4Pb2Bi(VO4)4 (OH)3 · 8H2O, has demonstrated that it is not a valid independent mineral species. Analyses of the type material and of additional samples by means of electron microprobe, X-ray powder and single-crystal diffractometry including structure refinements, and transmission electron microscopy have shown that duhamelite belongs to the adelite-descloizite-group with the general formula AB(XO4)(OH). Duhamelite in the strict sense corresponds to a bismuth- and calcium-bearing mottramite; the empirical formula of the type material is (Pb0.49Bi0.36Ca0.12)S0.97Cu1.01[(VO4)0.85 (AsO4)0.08(SiO4)0.07]S1.00[O0.27(OH)0.71]S0.98 (based on 5 oxygen atoms per formula unit), or simplified (Pb,Bi,Ca)Cu(VO4)(OH,O). The formal discreditation of duhamelite has been approved by the Commission on New Minerals and Mineral Names, I.M.A.

Neustädtelite and cobaltneustädtelite, two new minerals related to medenbachite, were found on samples from the dumps of the Güldener Falk mine near Schneeberg-Neustädtel, Saxony, Germany. The general appearance of the two new minerals is very similar: small tabular crystals up to 0.2 mm in diameter, transparent to translucent, with a brown color and a light brown streak; the lustre is adamantine. Both minerals are optically biaxial negative, 2V = 65(5)°, nx= 2.02(2), ny= 2.09 (calc.), nz= 2.12(2); pleochroism is strong with X = brown to opaque, Y = yellow, Z = pale yellow. Mohs’ hardness is 4.5. The cleavage parallel to {001} is good. The chemical compositions were derived by means of electron-microprobe analyses. Average contents for neustädtelite/cobaltneustädtelite are (in wt%): Bi2O352.58/51.54, PbO 0.08/0.08, CaO 0.15/0.32, Fe2O313.92/10.90, Al2O30.29/0.07, CoO 3.35/5.47, NiO 0.34/1.61, ZnO 0.09/0.39, CuO 0.07/0.00, As2O526.82/25.91, P2O50.23/0.43, H2O (calc.) 2.56/3.01, total 100.48/99.73. Mössbauer spectra of cobaltneustädtelite and medenbachite confirmed that all of the iron is trivalent. Based on 12 O atoms, the empirical formulae for the neustädtelite and cobaltneustädtelite type materials are (Bi1.94Ca0.02)∑1.96Fe1.00(Fe0.50Co0.38Ni0.04Al0.05Zn0.01Cu0.01)∑0.99[(OH)2.44O1.40]∑3.84[(AsO4)2.01(PO4)0.03]∑2.04and (Bi1.91Ca0.05)∑1.96Fe1.02(Co0.63Fe0.16Ni0.19Zn0.04Al0.01)∑1.03[(OH)2.88O1.12]∑4.00[(AsO4)1.95(PO4)0.05]∑2.00, respectively. As derived from chemical analyses and crystal-structure investigations the ideal end-member compositions are Bi2Fe3+Fe3+O2(OH)2(AsO4)2(neustädtelite) and Bi2Fe3+Co2+O(OH)3(AsO4)2(cobaltneustädtelite). Extensive solid solution is observed between these two minerals. Neustädtelite and cobaltneustädtelite crystallize in space group P1̅; the cell parameters refined from powder data are a = 4.556(1)/9.156(1), b = 6.153(2)/6.148(1), c = 8.984(2)/9.338(1) Å, α = 95.43(2)/83.24(1), β = 99.22(2)/70.56(1), γ = 92.95(3)/86.91(1)°, V = 246.9/492.2 Å3, Z = 1/2, density (calc.) 5.81/5.81 g/cm3. Structure investigations were performed using single-crystal X-ray data. In both minerals edge-sharing alternating Fe3+Ø6and (Fe3+,Co2+)Ø6/(Co2+,Fe3+)Ø6octahedra (Ø = O,OH) form chains parallel to [010] that are corner-linked by arsenate tetrahedra to layers parallel to (001). The Bi atoms are linked by O atoms to form columns parallel to [100]; these are sandwiched between layers of composition [6]M2(OH)2(AsO4)2(M = Fe3+,Co2+). In neustädtelite the Bi atoms are site disordered; in cobaltneustädtelite half of the Bi atoms are ordered and half are on a split position. The partial ordering is induced by the presence of three OH groups, as compared to two in neustädtelite. A structural reinvestigation of medenbachite, Bi2Fe3+ (Cu2+,Fe3+)(O,OH)2(OH)2(AsO4)2, proved isotypy with cobaltneustädtelite; the new cell parameters for medenbachite (refined from X-ray powder data) are: a = 9.162(2), b = 6.178(1), c = 9.341(2) Å, α = 83.50(2), β = 71.04(2), γ = 85.15(2)∞, V = 496 Å3, Z = 2.

Neustädtelite and cobaltneustädtelite, two new minerals related to medenbachite, were found on samples from the dumps of the Güldener Falk mine near Schneeberg-Neustädtel, Saxony, Germany. The general appearance of the two new minerals is very similar: small tabular crystals up to 0.2 mm in diameter, transparent to translucent, with a brown color and a light brown streak; the lustre is adamantine. Both minerals are optically biaxial negative, 2V = 65(5)°, nx= 2.02(2), ny= 2.09 (calc.), nz= 2.12(2); pleochroism is strong with X = brown to opaque, Y = yellow, Z = pale yellow. Mohs’ hardness is 4.5. The cleavage parallel to {001} is good. The chemical compositions were derived by means of electron-microprobe analyses. Average contents for neustädtelite/cobaltneustädtelite are (in wt%): Bi2O352.58/51.54, PbO 0.08/0.08, CaO 0.15/0.32, Fe2O313.92/10.90, Al2O30.29/0.07, CoO 3.35/5.47, NiO 0.34/1.61, ZnO 0.09/0.39, CuO 0.07/0.00, As2O526.82/25.91, P2O50.23/0.43, H2O (calc.) 2.56/3.01, total 100.48/99.73. Mössbauer spectra of cobaltneustädtelite and medenbachite confirmed that all of the iron is trivalent. Based on 12 O atoms, the empirical formulae for the neustädtelite and cobaltneustädtelite type materials are (Bi1.94Ca0.02)∑1.96Fe1.00(Fe0.50Co0.38Ni0.04Al0.05Zn0.01Cu0.01)∑0.99[(OH)2.44O1.40]∑3.84[(AsO4)2.01(PO4)0.03]∑2.04and (Bi1.91Ca0.05)∑1.96Fe1.02(Co0.63Fe0.16Ni0.19Zn0.04Al0.01)∑1.03[(OH)2.88O1.12]∑4.00[(AsO4)1.95(PO4)0.05]∑2.00, respectively. As derived from chemical analyses and crystal-structure investigations the ideal end-member compositions are Bi2Fe3+Fe3+O2(OH)2(AsO4)2(neustädtelite) and Bi2Fe3+Co2+O(OH)3(AsO4)2(cobaltneustädtelite). Extensive solid solution is observed between these two minerals. Neustädtelite and cobaltneustädtelite crystallize in space group P1̅; the cell parameters refined from powder data are a = 4.556(1)/9.156(1), b = 6.153(2)/6.148(1), c = 8.984(2)/9.338(1) Å, α = 95.43(2)/83.24(1), β = 99.22(2)/70.56(1), γ = 92.95(3)/86.91(1)°, V = 246.9/492.2 Å3, Z = 1/2, density (calc.) 5.81/5.81 g/cm3. Structure investigations were performed using single-crystal X-ray data. In both minerals edge-sharing alternating Fe3+Ø6and (Fe3+,Co2+)Ø6/(Co2+,Fe3+)Ø6octahedra (Ø = O,OH) form chains parallel to [010] that are corner-linked by arsenate tetrahedra to layers parallel to (001). The Bi atoms are linked by O atoms to form columns parallel to [100]; these are sandwiched between layers of composition [6]M2(OH)2(AsO4)2(M = Fe3+,Co2+). In neustädtelite the Bi atoms are site disordered; in cobaltneustädtelite half of the Bi atoms are ordered and half are on a split position. The partial ordering is induced by the presence of three OH groups, as compared to two in neustädtelite. A structural reinvestigation of medenbachite, Bi2Fe3+ (Cu2+,Fe3+)(O,OH)2(OH)2(AsO4)2, proved isotypy with cobaltneustädtelite; the new cell parameters for medenbachite (refined from X-ray powder data) are: a = 9.162(2), b = 6.178(1), c = 9.341(2) Å, α = 83.50(2), β = 71.04(2), γ = 85.15(2)∞, V = 496 Å3, Z = 2.

Schneebergite and nickelschneebergite are new members of the tsumcorite group; they represent the bismuth analogues of cobaltlotharmeyerite and nickellotharmeyerite. The two minerals were discovered on samples from the former mining area “Am Roten Berg“, Schneeberg, Saxony, Germany; associated minerals are scorodite, barium-pharmacosiderite, ferrilotharmeyerite (cobaltoan, bismuthian), preisingerite, and waylandite. Schneebergite and nickelschneebergite are very similar in appearance; they form crystal aggregates up to 1 mm and small tabular crystals (= 0.5 mm), elongated parallel to [010]. The colour is brown to beige (depending on the iron content), the streak is pale brown; Vickers hardness is VHN15 = 250 kg/mm2 corresponding to a Mohs' hardness of 4 to 4½. Crystallographic forms are {201} (dominant), {001}, {101}, {101}, {102}, {111}. The optical orientation is Y parallel to [010], X ˜ [001], pleochroism is weak to distinct (depending on the iron content) with X = Z = pale yellow and Y = brown (for both minerals). Schneebergite is biaxial positive, 2V = 85(5)°, nx = 1.93(calc.), ny = 1.95(1), and nz = 1.98(2); nickelschneebergite is biaxial negative, 2V = 77(5)°, nx = 1.92(calc.), ny = 1.95(1), and nz = 1.97(2). Empirical formulas calculated from electron microprobe analyses and based on 10 oxygen atoms are (Bi0.74Ca0.29)S1.03(Co1.06Ni0.75Fe0.22)S2.03 [(AsO4)1.99(SO4)0.01]S2.00\[(OH)1.09(H2O)0.91]S2.00 for schneebergite, and (Bi0.73Ca0.28Pb0.01)S1.02(Ni1.18Co0.64Fe0.16)S1.98(AsO4)1.99 [(H2O)1.10(OH)0.93]S2.03 for nickelschneebergite; the ideal formulas are BiCo2(AsO4)2\[(H2O)(OH)] and BiNi2(AsO4)2 [(H2O)(OH)], respectively. There is a probably complete solid solution involving schneebergite, nickelschneebergite, cobaltlotharmeyerite, and nickellotharmeyerite. Schneebergite/nickelschneebergite are monoclinic, space group C2/m, with a = 9.005(1)/8.995(1), b = 6.211(1)/6.207(1), c = 7.440(1)/7.462(1) Å, ß = 115.19(1)/115.00(1)°, V = 376.5(1)/377.6(1) Å3, Z = 2, Dcalc = 5.28/5.23 g/cm3. Structure investigations for schneebergite (R1 = 0.038) and nickelschneebergite (R1 = 0.044) based on single-crystal X-ray data confirmed isotypy with the tsumcorite-type structure.

Abstract Using a method of preparing polished thin-sections described in this paper, we are able to detect microdiamonds in high-pressure metamorphic rocks quickly and quantitatively by a distinctive striation pattern on the polished surface of the thin-section. We present results on samples from diamondiferous gneiss and marble of the Lake Kumdy-Kol region of the Kokchetav Massif, Northern Kazakhstan. Our method clearly reveals microdiamonds as small as l µm by a striation pattern as soon as they emerge on the surface during the polishing procedure. The striation pattern on the polished surface disappears almost immediately after extraction of the microdiamond that caused it. More than six hundred polished thin-sections of various kinds of igneous and metamorphic rocks mostly without a high-pressure origin were examined, but this type of striation pattern was found in less than 1 % of these. In such examples the striations could also be due to the contamination of diamond from external sources.

Abstract The general formula for the tsumcorite-group minerals is Me(l)Me(2)2(XO4)2(OH,H2O)2; Me(l) = Pb, Ca, Na, and partly Bi; Me(2) = Fe, Mn, Cu, Zn, Co, Ni, and partly Al; X = P, As, V, S. Out of this group the minerals ferrilotharmeyerite, tsumcorite, thometzekite (sulfatian), mounanaite, helmutwinklerite, gartrellite and zincian gartrellite were investigated regarding optical properties, morphology, chemical composition, infrared and Mossbauer spectroscopy, and crystal structure. Crystal symmetry is either (i) triclinic in the case of an ordered occupation of two Me(2) sites, (ii) triclinic due to ordering of the hydrogen bonds in the case of species with 2 water molecules per formula unit or (iii) monoclinic in the other cases. Cell parameters were refined from X-ray powder data; powder patterns are given for thometzekite (sulfatian), mounanaite, helmutwinklerite, gartrellite and zincian gartrellite. Mossbauer measurements confirmed the iron in ferrilotharmeyerite, tsumcorite, gartrellite and zincian gartrellite to be completely trivalent. Electron microprobe analyses showed that at least partial solid solution is common for the Me(2) and less frequent for the X and Me(l) site. In addition to homovalent substitutions [e.g. Zn2+ ? Cu2+ or (ASO4)3- ? (PO0)3-] there are 3 heterovalent exchange mechanisms with a coupled substitution involving OH/H2O groups: (i) on the Me(l) site, e.g. [(Ca)2+(H2O)]2+ ? [(Bi)3+(OH)-]2+, (ii) on the Me(2) site, e.g. [(Zn,Cu,Co,Ni)2+(H2O)]2+ ? [(Fe,Al,Mn)3+(OH)]2+, and (iii) on the X site, e.g. [(AsO4)3-(H2O)]3- ? [(SO4)2-(OH)-]3-. Crystals of ferrilotharmeyerite, tsumcorite, thometzekite (sulfatian), and mounanaite have monoclinic symmetry, space group C2/m. The crystal structures were investigated by single-crystal X-ray diffraction. The structural data for tsumcorite given by Tillmanns & Gebert (1973) were confirmed, for the other minerals isotypy is proved. Infrared absorption spectra indicate two independent and strong hydrogen bonds. In particular, there is no evidence for protonated arsenate groups. The chemical formulas of ferrilotharmeyerite and lotharmeyerite (for analogy reasons) have to be revised on a 10 oxygen basis to Ca(Fe3+,Zn)2(AsO4)2(OH,H2O)2, and Ca(Mn3+,Zn)2 (AsO4)2(OH,H2O)2, respectively. The triclinic members of the tsumcorite group are gartrellite, zincian gartrellite, phosphogartrellite, helmutwinklerite, and probably (sulfate-free) thometzekite; the space group is P1¯, with a pronounced monoclinic C-centered pseudoctW. A redefinition based on type material was performed for gartrellite; it has the ideal formula PbCuFe3+(AsO4)2(OH)(H2O), but it frequently contains substantial amounts of Zn (at least up to 12.6 wt.% ZnO), whereas the ratio Cu:Fe is close to 1:1. The triclinic distortion is caused by an ordered arrangement of Fe[6]O6 octahedra and tetragonal bi-pyramidal Cu[4+2]O6 polyhedra, as shown by Rietveld refinement of powder data. The weak superstructure reflections of helmutwinklerite observed by single-crystal X-ray investigations are obviously caused by an ordering of the hydrogen bonds.