Werner H. Paar

A new mineral, chrisstanleyite, Ag2Pd3Se4, from Hope's Nose, Torquay, Devon, England

Abstract Chrisstanleyite, Ag2Pd3Se4, is a new mineral from gold-bearing carbonate veins in Middle Devonian limestones at Hopes Nose, Torquay, Devon, England. It is associated with palladian and argentian gold, fischesserite, clausthalite, eucairite, tiemannite, umangite, a Pd arsenide-antimonide (possibly mertieite II), cerussite, calcite and bromian chlorargyrite. Also present in the assemblage is a phase similar to oosterboschite, and two unknown minerals with the compositions, PdSe2 and HgPd2Se3. Chrisstanleyite occurs as composite grains of anhedral crystals ranging from a few lam to several hundred μm in size. It is opaque, has a metallic lustre and a black streak, VHN100 ranges from 371-421, mean 395 kp/mm2 (15 indentations), roughly approximating to a Mohs hardness of 5. Dcalc = 8.308 g/cm3 for the ideal formula with Z = 2. In plane-polarised reflected light, the mineral is very slightly pleochroic from very light buff to slightly grey-green buff, is weakly bireflectant and has no internal reflections. Bireflectance is weak to moderate (higher in oil). Anisotropy is moderate and rotation tints vary from rose-brown to grey-green to pale bluish grey to dark steel-blue. Polysynthetic twinning is characteristic of the mineral. Reflectance spectra and colour values are tabulated. Very little variation was noted in eleven electron-microprobe analyses on five grains, the mean is: Ag 25.3, Cu 0.17, Pd 37.5, Se 36.4, total 99.37 wt.%. The empirical formula (on the basis of ∑M + Se = 9) is (Ag2.01Cu0.02)∑2.03 Pd3.02Se3.95, ideally Ag2Pd3Se4 . Chrisstanleyite is monoclinic, a 6.350(6), b 10.387(4), c 5.683(3) Å, β 114.90(5)° space group P21/m (11) or P21(4). The five strongest X-ray powder-diffraction lines [d in Å (I)(hkl)] are: 2.742 (100) (-121), 2.688 (80) (-221), 2.367 (50) (140), 1.956 (100) (-321,150) and 1.829 (30) (-321,042). The name is in honour of Dr Chris J. Stanley of The Natural History Museum in London. The mineral and its name have been approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association.

Verbeekite, monoclinic PdSe2, a new mineral from the Musonoi Cu-Co-Mn-U mine, near Kolwezi, Shaba Province, Democratic Republic of Congo

Abstract Verbeekite, ideally PdSe2, monoclinic with space-group choices C2/m, C2 or Cm; a = 6.659(7), b = 4.124(5), c = 4.438(6) Å, β = 92.76(3)8, V = 121.7(4) Å3; a:b:c = 1.6147:1:1.0761, Z = 2, is a new, very rare, primary mineral, intimately associated with secondary oosterboschite {(Pd,Cu)7Se5}, from the Musonoi Cu-Co-Mn-U mine, near Kolwezi, Shaba Province, Democratic Republic of Congo. Additional associated minerals are Cu- and Pd-bearing trogtalite {(Co,Cu,Pd)Se2}, Se-bearing digenite and Se-bearing covellite. The strongest five lines of the X-ray powder-diffraction pattern {d in Å (I) (hkl)} are: 4.423(30)(001), 3.496 (30)(110), 2.718(100)(111), 1.955(50)(310) and 1.896(50)(1̄12). The mineral has also been identified, as a single anhedral 25 μm-sized grain, from Hope’s Nose, Torquay, Devon, England where it is associated with native gold, chrisstanleyite Ag2Pd3Se4, oosterboschite(?), unnamed Pd2HgSe3 and cerussite. At Musonoi, altered verbeekite grains do not exceed 200 μm in size and are anhedral, black, with a black streak and a metallic lustre. The mineral is opaque, brittle, has an uneven fracture, and lacks discernible cleavage. The VHN5 ranges 490-610, mean 550 kp/mm2 (2 indentations), roughly approximating a Mohs’ hardness of 5Ý. Dcalc. = 7.211 g/cm3 for the ideal formula. Electron-microprobe analyses (mean of 4 spot analyses) yielded Pd 39.6, Cu 0.5, Se 58.8, total 98.9 wt.%. The empirical formula is (Pd0.99Cu0.02)∑1.01Se1.99, based on Pd+Cu+Se = 3. In plane-polarized reflected light, the mineral is a nondescript grey and is neither pleochroic nor perceptibly bireflectant. Anisotropy is moderate with rotation tints in varying shades of brown. Reflectance spectra and colour values are tabulated. The name honours Dr Théodore Verbeek (1927-1991) who was the first geoscientist to study the Musonoi palladium mineralization in the Democratic Republic of Congo (1955-1967) and who co-discovered this new mineral phase.

The new mineral baumstarkite and a structural reinvestigation of aramayoite and miargyrite

Abstract Baumstarkite is a new mineral found coating miargyrite from the San Genaro mine, Huancavelica Department, Peru. It is triclinic and the third naturally occurring modification of AgSbS2 besides monoclinic miargyrite and cubic cuboargyrite. The composition is usually close to the ideal formula. However, some grains of baumstarkite show zoned lamellae with As contents up to 11.5 wt% and accords to Ag3(Sb,As)2SbS6. Baumstarkite is isotypic with aramayoite [end-member composition Ag3Sb2BiS6; solid solutions require the extended formula Ag3Sb2(Bi,Sb)S6]. Single-crystal X-ray structure investigations were performed for baumstarkite [type locality, a = 7.766(2), b = 8.322(2), c = 8.814(2) Å, α = 100.62(2), β = 104.03(2), γ = 90.22(2)°, Z = 2{Ag3Sb3S6}, space group P1̅, R1(F) = 0.057, wR2(F2) = 0.128], aramayoite [Armonia mine, El Quevar, Argentinia: a = 7.813(2), b = 8.268(2), c = 8.880(2) Å, α = 100.32(2), β = 104.07(2), γ = 90.18(2)°, Z = 2{Ag3Sb2S6}, space group P1̅, R1(F) = 0.034, wR2(F2) = 0.084], and miargyrite associated with baumstarkite type material [a = 12.862(3), b = 4.409(1), c = 13.218(3) Å, β = 98.48(2)°, Z = 8{AgSbS2}, space group C2/c, R1(F) = 0.031, wR2(F2) = 0.082]. The space-group symmetries of aramayoite and miargyrite were revised, and the refinements unambiguously showed that the three investigated minerals are centrosymmetric. In baumstarkite and aramayoite each three atomic sites are occupied by Ag and M = As, Sb, Bi, respectively. The Ag atoms have two short bonded ligands (Ag-S is 2.51 to 2.58 Å). The M1 and M2 sites are [3 + 3] coordinated and are predominantly occupied by (Sb, As) atoms (M-S = 2.44 to 2.54 Å and > 3.09 Å). The [2 + 2 + 2] coordination of the M3 atom differs in the two mineral species: the two shortest bond lengths in baumstarkite are smaller (2.51 Å) than in aramayoite (2.64 Å) to allow for the different sizes of the Sb and Bi atoms, respectively; the medium bond lengths are similar (2.75 to 2.82 Å) and the longest bond lengths are > 3.02 Å. Considering only the nearest-neighbor environments, baumstarkite and aramayoite feature zigzag chains parallel to [010], which are linked together to form layers parallel to (001). In miargyrite [2 + 2] and [2] coordinated Ag atoms are linked by SbS3 pyramids to form a three-dimensional network.

The crystal structure of synthetic buckhornite, (Pb2BiS3)(AuTe2)

Synthetic buckhornite, [Pb2BiS3][AuTe2], was grown from melts in connection with the search for high-temperature superconductive materials. Chemical analyses were performed by electron-microprobe investigations. The crystal structure was determined from 726 single-crystal X-ray reflections of a twinned crystal. The refinement gave R(F)=0.101 for 33 variable parameters. The space group is Pmmn, a=4.108(3) Å, b=12.308(9) Å, c=9.331(6) Å, Z=2. The atomic arrangement features a pronounced layer structure formed by two different sheets. (a) Planar Au[4Te]Te4 configurations are edge-connected to ribbons in [100]; they are linked by Te···Te contacts to planar nets parallel to (001). Te and Au atoms are in a distorted square arrangement. (b) Slices of (Pb,Bi)S are sandwiched between these AuTe2 layers. They form SnS-archetype layers. The present paper proves that buckhornite, [(Pb2Bi)Σ3S3] [(Te2Au)Σ3], and nagyagite, [(Pb3(Pb,Sb)3)Σ6S6][(Te,Au)3] are members of a homologous series. Both compounds have comparable Au—Te layers. However, ordering of Au and Te atoms was verified in buckhornite only. In buckhornite two (Pb,Bi)S sheets form one slice of the SnS-archetype whereas in nagyagite four (Pb,Sb)S layers form the corresponding slice with a thickness of two SnS-archetype slabs.

Pb−Bi−(Cu)-sulfosalts in Paleozoic gneisses and schists from Oberpinzgau, Salzgurg province, Austria

Pb−Bi−(Cu)-sulfosalts occur as minor minerals widely distributed in rocks of the Penninic unit (gneisses, schists, metavolcanics, etc.), Oberpinzgau, Salzburg. The sulfosalts have been investigated by ore microscopy, X-ray diffraction and electron microprobe analysis. The phases identified are: heyrovskyite, cosalite (Moaralm, Sedl, and Wiesbachrinne in the Habach Valley), lillianite (Moaralm, Sedl; Modereck near the Fuscher Valley), galenobismutite (Barenbad in the Hollersbach Valley) and Bi-bearing galena. Heyrovskyite (Moaralm) has a composition close to Pb6Bi2S9, with Ag contents between 0.2 (Sedl) and 0.6 (Moaralm) wt.%. Lillianite has the composition Pb2.86–2.91 Bi2.08–2.17Ag0.04–0.08 S6, and cosalite, Pb1.81–2.04 Bi1.92–2.02 Ag0.02–0.06 Cu0.11–0.18S5. The average chemical composition of galenobismutite is Pb1.25Bi1.6Sb0.1Cu0.1Ag0.02Fe0.1S4. Needle-like inclusions of a joseite-type mineral, “joseite-A” (Bi,Pb)4.01 Te0.9S2.08, and irregular to needle-like grains of native bismuth usually occur along the elongation direction of the lath-like galenobismutite crystals.

Suredaite, PbSnS3, a new mineral species, from the Pirquitas Ag-Sn deposit, NW-Argentina: mineralogy and crystal structure

Abstract Suredaite, ideally PbSnS3, is a new mineral species from the Pirquitas Ag-Sn deposit (Province Jujuy, NW-Argentina). It was observed in symmetrically banded veins in the Oploca district, and is associated with sphalerite, arsenopyrite, pyrite-marcasite, cassiterite, cylindrite, franckeite, hocartite, rhodostannite, and various Ag-Sb and Ag-Bi sulfosalts in minor amounts. Suredaite occurs in layers up to 1 cm in thickness as aggregates of radially arranged tabular-prismatic (single) crystals, has a metallic lustre, and a dark grey streak. VHN50 ranges between 18.2 and 20.6 (mean 19.6) GPa, the Mohs hardness is 2.5-3. It has perfect cleavages parallel to {001}, {101}, and {100}. The measured density varies between 5.54 and 5.88 g/cm3, Dx was determined to be 5.615 g/cm3. In reflected plane-polarised light, it is white and is not perceptibly bireflectant or pleochroic. It lacks internal reflections and is weakly anisotropic with metallic blue, mauve to brown rotation tints. Specular reflectance percentages in air and in oil are tabulated from 400 to 700 nm and compared graphically with those for the type specimen of teallite, PbSnS2. Electron microprobe analyses showed suredaite to be chemically inhomogeneous with respect to the compositional variations (in wt%): Pb 42.3- 48.5, Ag 0.3-1.1, Fe 0.3-1.0, As 0.2-2.1, Sn 27.7-30.2, S 23.1-24.7. The crystal structure determined from single-crystal X-ray diffraction data revealed orthorhombic symmetry [space group Pnma, Z = 4, a = 8.8221(3), b = 3.7728(3), c = 14.0076(3) Å; V = 466.23(4) Å3]. The atomic arrangement is isostructural to the NH4CdCl3 structure type which exists in a series of isotypic sulfides and selenide compounds. The suredaite structure, which is the natural analogue of synthetic PbSnS3, consists of columns of double-edge sharing octahedra running parallel to the b axis, which house the Sn atoms. These columns are linked by rods of eightfold-coordinated Pb atoms. On the basis of the structure determination, the empirically determined idealized formula follows a [8](Pb, As,Ag, Sn) [6](Sn,Fe)S3 stoichiometry. Crystalchemical arguments suggest Ag possibly to occupy interstitial sites according to the alternative formula [4](⃞,Ag) [8](Pb, As, Sn) [6](Sn,Fe) S3. The name of this new mineral species is in honor of R.J. Sureda Leston, head of the Department of Mineralogy and Economic Geology, University of Salta, Argentina.

Daliranite, PbHgAs 2 S 6 , a new sulphosalt from the Zarshouran Au-As deposit, Takab region, Iran

Abstract Daliranite, ideally PbHgAs2S6, occurs as a rare sulphosalt species at the Carlin-type Zarshouran Au-As deposit North of the town of Takab in the Province of West Azarbaijan, Iran. The new species is associated with orpiment, rarely with galkhaite, hutchinsonite and cinnabar. The strongly silicified matrix of the specimens has veinlets of sphalerite, with rare inclusions of galena and various (Cu)-Pb-As(Sb) sulphosalts. Daliranite occurs as matted nests of acicular and flexible fibres up to 200 μm in length and a width less than a few μm. The colour is orange-red with a pale orange-red streak and the lustre is adamantine. The mineral is transparent and does not fluoresce. The Mohs hardness is <2. Electron microprobe analyses give the empirical formula Pb0.95Tl0.01Hg1.04As2.10S5.91, ideally PbHgAs2S6; the calculated density is 5.93 g cm−3. Unit-cell parameters were determined by an electron-diffraction study and refined from X-ray powder data. Daliranite is monoclinic primitive with a = 19.113(5) Å, b = 4.233(2) Å, c = 22.958(8) Å, β = 114.78(5)°, V = 1686.4 Å3 and Z = 8, a:b:c = 4.515:1:5.424, space group P2, Pm or P2/m. The strongest X-ray powder-diffraction lines [d in Å, (I), (hkl)] are: 8.676, (80), (200); 4.654, (50), (4̅01); 3.870, (40), (2̅11); 3.394, (50), (113); 3.148, (40b), (6̅02); 2.892, (50), (6̅00); 2.724, (100), (7̅03); 2.185, (50), (3̅19). The formula shows a sulphur excess which may correspond to S-S bonding (persulphide). The new sulphosalt is a late phase in the crystallization sequence, and was formed after orpiment, contemporaneously with quartz II, at a temperature between 157 and 193°C. The name honours Dr Farahnaz Daliran (University of Karlsruhe, Germany) in recognition of her outstanding contributions to research on ore deposits, especially Au, Zn and Fe, in Iran.

New discovery of epithermal gold at Chahnali prospect, Bazman volcano, SE-Iran

Recent exploration in the region of Bazman in SE-Iran led to the discovery of gold mineralization in different prospects. The epithermal gold mineralization at Chahnali prospect is hosted by late Tertiary andesites and dacites which had been affected by a widespread and intense alteration including propylitization, argillitization, and silicification. The propylitization was of regional scale and predated the mineralizing events.

Vein type Ag-(Au)-Pb, Zn, Cu-(W,Sn) mineralization in the Southern Kreuzeck Mountains, Carinthia Province, Austria

SummaryThe Early Paleozoic Altkristallin of the Kreuzeck Mountains is well-known for its mostly small gold, silver, copper, lead, zinc, antimony, and mercury deposits. A detailed investigation of silver(-gold)-base metal mineralizations (Plattach, Niedermülleralm, Grakofel and DraBnitz) is presented in this paper. The deposits are structurally controlled. Faults and shear zones penetrate garnet-mica schists, gneisses (partly at Grakofel), and amphibolites (partly at DraBnitz). In places the mineralization occurs at the sheared contact between quartz porphyrite dykes (K/Ar ages of 30–40 Ma) and country rocks (e.g. at Niedermülleralm).The precious metal mineralization occurs as bundles of quartz veins, which were mined over a distance of 150-200 m along strike and dip. The depositional textures such as vugs, symmetrical banding, cockade and colloform structures clearly indicate open space filling. The mineral parageneses of Plattach, Niedermülleralm and Grakofel ores are similar to each other, but distinctly different from that of the DraBnitz deposit. The first mentioned deposits are characterized by abundant silver sulfosalts such as freibergite (21.7–36.3 wt.% Ag), pyrargyrite, miargyrite, diaphorite (Pb1 7−1.8Ag2.9−3.2Sb2.8−3.0S8), owyheeite (Ag2.69Pb9.44Sb10.38S28) and stephanite, as well as sphalerite and galena (100–1600 ppm Ag); hocartite ( ∼ [Ag, Cu]2 [Fe, Zn] SnS4) is intergrown with pyrargyrite and occurs as inclusions in pyritic ores at Niedermülleralm. Pyrite, arsenopyrite, and chalcopyrite are present in minor amounts. Au-Ag alloys with Ag contents ranging between 40.4–49.5 wt.% (electrum) and 73.5–74.2 wt.% (aurian silver) have grain sizes between 2 and 60 pin and are frequently associated with freibergite, pyrite and quartz.Draßnitz is a silver bearing base metal deposit with a possible but not proved silver enrichment in the uppermost ∼ 100 m of the vein system. Arsenopyrite, pyrrhotite, chalcopyrite, sphalerite, bournonite, Ag-tetrahedrite, and galena are the dominant ore minerals, locally accompanied by substantial amounts of zincian stannite (∼25 mol.% kesterite), ferberite, scheelite, and minor amounts of molybdenite, native bismuth, ullmannite and a silver sulfosalt.The most common types of hydrothermal wall-rock alteration are phyllic alteration (sericitization), silicification, carbonatization, and sulfidization. The alteration zone does not exceed a few decimeters on both sides of the veins.Fluid inclusion studies of quartz reveal formation temperatures of 165–250°C (Plattach) and 165–220°C (Niedermülleralm). The corresponding data for the Grakofel and Draßnitz ores are 180–330°C and 210–365°C, respectively. The salinities vary between 3–7 equiv. wt.-% NaCl (Niedermülleralm, Plattach, Draßnitz) and 4–13.3 equiv. wt.-% NaCl (Grakofel).A shallow-seated plutonic or subvolcanic magma (quartz porphyrite?) could be the reason for telescoping, different temperatures and heat gradient within the mineralized zone. The isotope compositions of the fluids give evidence for their metamorphic origin, probably contaminated by a minor meteoric component.ZusammenfassungDas altpaläozoische Altkristallin der Kreuzeckgruppe beherbergt eine große Zahl zumeist kleiner Gold-, Silber-, Kupfer-, Blei-, Zink-, Antimon- und Quecksilber-Lagerstätten. In dieser Arbeit werden detaillierte Untersuchungen von Silber(-Gold)-Buntmetall-Vererzungen (Plattach, Niedermülleralm, Grakofel und Draßnitz) vorgestellt. Die Lagerstätten sind strukturkontrolliert; Verwerfungs- und Scherzonen setzen in Granat-glimmerschiefern, Gneisen (teilweise Grakofel) und Amphiboliten (teilweise Draßnitz) auf. Bereichsweise tritt die Vererzung am zerscherten Kontakt zwischen Quarzporphyritgängen (K/Ar-Alter 30–40 Ma) und dem Nebengestein auf (z.B. Niedermülleralm).Die edelmetallhältige Vererzung ist an Quarzgang-Systeme gebunden, deren Ausdehnung aufgrund der bergbaulichen Aktivitäten kaum mehr als 150–200 m im Streichen und Einfallen betragen haben dürfte. Die beobachteten Ablagerungstexturen mit zahlreichen Drusen, symmetrischen Bänderungen, Kokarden- und kolloformen Strukturen sind eindeutige Indizien für eine Kristallisation in Hohlräumen. Die Mineral-paragenesen der Reviere Plattach-Niedermülleralm und des Grakofels sind einander sehr ähnlich, unterscheiden sich aber deutlich von jenen der Draßnitz. Die erstgenannten Lagerstätten zeichnen sich durch das bevorzugte Auftreten von Silber-Sulfosalzen, wie Freibergit (21,7–36,3 Gew.% Ag), Pyrargyrit, Miargyrit, Diaphorit (Pb1,7−1,8Ag2,9−3,2 Sb2,8−3,0S8), Owyheeit (Ag2. 69Pb9 ,44Sb10,38S28) und Stephanit sowie Sphalerit und Galenit (100–1600 ppm Ag) aus; Hocartit (∼ [Ag, Cu]2 [Fe, Zn] SnS4), der mit Pyrargyrit verwachsen ist, bildet Einschlüsse in Pyriterzen der Niedermülleralm. Zu geringeren Teilen kommen Pyrit, Arsenopyrit und Chalkopyrit vor. Gold-Silber-Legierungen mit Ag-Gehalten zwischen 40,4–49,5 Gew.% (Elektrum) und 73,5–74,2 Gew.% (Au-hältiges Silber) und Korngrößen zwischen 2 und 60 Mm sind häufig mit Freibergit, Pyrit und Quarz assoziiert.Die Lagerstätten der Draßnitz enthalten eine silberführende Buntmetallvererzung mit einer aufgrund der alten Bergbautätigkeit nur vermutbaren ehemaligen Silber-Reicherzzone in den obersten Gangabschnitten (Mächtigkeit ca. 100 m). Die Haldenerze bestehen heute aus Arsenopyrit, Pyrrhotin, Chalkopyrit, Sphalerit, Bournonit, Ag-Tetraedrit und Galenit; sie werden bereichsweise von beträchtlichen Anteilen an Zn-Stannit (∼25 Mol.% Kesterit), Ferberit, Scheelit, sowie in geringen Mengen von gediegenem Wismut, Ullmannit und Ag-Sulfosalzen begleitet.Serizitisierung, Silizihzierung, Karbonatisierung und Sulfidisierung sind die wesentlichen hydrothermalen Nebengesteinsveränderungen. Die Alterationszone erreicht allerdings nur einige Dezimeter auf beiden Seiten der Erzgänge.Die aus Flüssigkeitseinschlüssen in Quarz ermittelten Bildungstemperaturen zeigen für die Plattach 165–250°C, für die Niedermülleralm 165–220T. Die entsprechenden Temperaturdaten für die Grakofel-Vererzung betragen 180–330°C und 210–365°C für die Draßnitz. Die Salinitäten schwanken zwischen 3–7 Gew.% NaCl äq. (Niedermülleralm, Plattach, Draßnitz) und 4–13,3 Gew.% NaCl äq. (Grakofel).Ein hochplutonisches oder subvulkanisches Magma (Quarzporphyrit?) könnte eine mögliche Erklärung für das Teleskoping, die Temperaturunterschiede und den Wärmegradienten innerhalb der Vererzungszone sein. Die Isotopenzusammensetzung der Fluide deutet auf deren metamorphen Ursprung mit vermutlich untergeordneter meteorischer Komponente hin.

Lammerit, Cu3[AsO4]2, ein neues Mineral von Laurani, Bolivien

Die chemische Analyse des neuenMMinerals Lammerit mit der Elektronenmikrosonde ergab: CuO 49,9, ZnO 0,8, MgO 0,2, FeO 0,2 und As2O5 49,8, Summe 100,9%. Aus diesem Ergebnis wurde die idealisierte Formel Cu3[AsO4]2 abgeleitet.