ALBERT

Description: Studying the reason for the formation of two structural sub-types, seven arsenate and vanadate compounds of descloizite and adelite groups [specifically ( 1 ) CdCo(OH)(AsO 4 ), ( 2 ) CdCu(OH)(AsO 4 ), ( 3 ) SrCo(OH)(AsO 4 ), ( 4 ) SrZn(OH)(AsO 4 ), ( 5 ) SrCu(OH)(VO 4 ), ( 6 ) CdCo(OH)(VO 4 ), and ( 7 ) CdCu(OH)(VO 4 ) (bold numbers throughout paper refer to these compounds)] were synthesized under low-temperature hydrothermal conditions. 1 – 2 and 6 – 7 are isostructural with descloizite, and 3 – 5 are with adelite-group minerals and several synthetic compounds. Together with a sample of conichalcite, (8) CaCu(OH)(AsO 4 ), they were investigated using single-crystal X-ray diffraction [ R ( F ) = 0.0153–0.0283 for 1 – 5 and 8 ; for 6 and 7 , R ( F ) = 0.0603 and 0.0444, respectively] and Raman spectroscopy. Although crystallizing in different orthorhombic space groups, the atomic arrangements of descloizite-( Pnam ) and adelite-( P 2 1 2 1 2 1 ) type compounds adopt the same topology: the atomic arrangement is characterized by M 2O 6 octahedrons ( M 2 = Mg 2+ , Al 3+ , Mn 2+,3+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ) edge-linked into chains. These chains are interconnected by X O 4 tetrahedrons ( X = Si 4+ , P 5+ , V 5+ , As 5+ , Mo 6+ ) into a three-dimensional framework. Cavities host M 1 atoms ( M 1 = Na + , Ca 2+ , Cd 2+ , Hg 2+ , Pb 2+ ); their coordination varies from 7 for descloizite-type representatives to 8 for adelite-type structures. The OH stretching frequencies in the Raman spectra are in good agreement with the observed O–H···O donor-acceptor distances. A detailed discussion of the crystal chemistry of these compounds and their influence on the space-group symmetry indicate a distinct dependence of the structural changes on the average ionic radii ( r M 1 + r X )/2.

Description: Vein-type Pb-Ni-Bi-Au-Ag mineralization at the Clemence deposit in the Kamariza and “km3” in the Lavrion area, was synchronous with the intrusion of a Miocene granodiorite body and related felsic and mafic dikes and sills within marbles and schists in the footwall of (and within) the Western Cycladic detachment system. In the Serpieri deposit (Kamariza area), a porphyry-style pyrrhotite-arsenopyrite mineralized microgranitic dike is genetically related to a garnet-wollastonite bearing skarn characterized by a similar base metal and Ni (up to 219 ppm) enrichment. The Ni–Bi–Au association in the Clemence deposit consists of initial deposition of pyrite and arsenopyrite followed by an intergrowth of native gold-bismuthinite and oscillatory zoned gersdorffite. The zoning is related to variable As, Ni, and Fe contents, indicating fluctuations of arsenic and sulfur fugacity in the hydrothermal fluid. A late evolution towards higher sulfur fugacity in the mineralization is evident by the deposition of chalcopyrite, tennantite, enargite, and galena rimming gersdorffite. At the “km3” locality, Ni sulfides and sulfarsenides, vaesite, millerite, ullmannite, and polydymite, are enclosed in gersdorffite and/or galena. The gersdorffite is homogenous and contains less Fe (up to 2 wt.%) than that from the Clemence deposit (up to 9 wt.%). Bulk ore analyses of the Clemence ore reveal Au and Ag grades both exceeding 100 g/t, Pb and Zn 〉 1 wt.%, Ni up to 9700 ppm, Co up to 118 ppm, Sn 〉 100 ppm, and Bi 〉 2000 ppm. The “km3” mineralization is enriched in Mo (up to 36 ppm), Ni (〉1 wt.%), and Co (up to 1290 ppm). Our data further support a magmatic contribution to the ore-forming fluids, although remobilization and leaching of metals from previous mineralization and/or host rocks, through the late involvement of non-magmatic fluid in the ore system, cannot be excluded.

Description: Four new alunite-type chromates, KSc 3 (CrO 4 ) 2 (OH) 6 , KIn 3 (CrO 4 ) 2 (OH) 6 , RbIn 3 (CrO 4 ) 2 (OH) 6 , and AgIn 3 (CrO 4 ) 2 (OH) 6 , have been prepared by mild hydrothermal synthesis at T = 220 °C as well-developed, thick tabular to pseudo-octahedral crystals with maximum dimensions between approximately 0.5 and 1 mm. The crystal structures were refined from single-crystal intensity data (Mo K α X-radiation, CCD area detector, 293 K, 2 max = 70°). The new members adopt the alunite parent structure-type (space group R 3 m , no. 166), with a = 7.763(1)/7.813(1)/7.817(1)/7.845(1), c = 17.575(3)/17.682(3)/18.075(3)/16.997(3) Å, V = 917.2(2)/934.8 (2)/956.5(2)/905.9(2) Å 3 ( Z = 3), and R ( F ) = 1.36 / 1.21 / 1.23 / 1.33%, respectively. The H atoms could be located in each compound. Hydrogen bonds are all within a very close range (O3...O1 = 2.959–3.020 Å). All alkali and Sc/In sites are fully occupied, and the alkali atoms do not show any positional disorder, unlike Ag which is distinctly off-origin in AgIn 3 (CrO 4 ) 2 (OH) 6 . Average bond-lengths are as follows: [12] K–O=3.003, [6] Sc–O = 2.106, [4] Cr–O = 1.653 Å (KSc member); [12] K–O=3.000, [6] In–O = 2.145, [4] Cr–O = 1.653 Å (KIn); [12] Rb–O=3.051, [6] In–O = 2.147, Cr–O = 1.653 Å (RbIn); and [9] Ag–O=2.826, [6] In–O= 2.142, [4] Cr–O = 1.648 Å (AgIn). The origin and possible meaning of a small, but conspicuous residual-density peak at (0, 0, 0.5) in the In members is discussed. These chromates represent the first structurally characterized Sc and In members of the large alunite supergroup, and may serve as analogues in future studies of naturally occurring Fe or sulfate members. Alunite-type Cs analogues could not be synthesized hydrothermally, in agreement with the fact that no natural or synthetic Cs compounds with the alunite topology have been reported so far. Instead, the syntheses yielded orthorhombic CsSc(CrO 4 ) 2 [CsCr 3+ (Cr 6+ O 4 ) 2 -type] and monoclinic CsIn(CrO 4 ) 2 [(NH 4 )Fe(CrO 4 ) 2 -type].

Description: Crystal-structure refinements in space group P21/c were performed on five grains of rathite with different types and degrees of thallium, silver, and antimony substitutions, as well as quantitative electron-microprobe analyses of more than 800 different rathite samples. The results of these studies both enlarged and clarified the complex spectrum of cation substitutions and the crystal chemistry of rathite. The [Tl+ + As3+] ↔ 2Pb2+ scheme of substitution acts at the structural sites Pb1, Pb2, and Me6, the [Ag+ + As3+] ↔ 2Pb2+ substitution at Me5, and the Sb-for-As substitution at the Me3 site only. The homogeneity range of rathite was determined to be unusually large, ranging from very Tl-poor compositions (0.16 wt%; refined single-crystal unit-cell parameters: a = 8.471(2), b = 7.926(2), c = 25.186(5) Å, β = 100.58(3)°, V = 1662.4(6) Å3) to very Tl-rich compositions (11.78 wt%; a = 8.521(2), b = 8.005(2), c = 25.031(5) Å, β = 100.56(3)°, V = 1678.4(6) Å3). The Ag content is only slightly variable (3.1 wt%–4.1 wt%) with a mean value of 3.6 wt%. The Sb content is strongly variable (0.20 wt%–7.71 wt%) and not correlated with the Tl content. With increasing Tl content (0.16 wt%–11.78 wt%), a clear increase of the unit-cell parameters a, b, and V, and a slight decrease of c is observed, although this is somewhat masked by the randomly variable Sb content. The revised general formula of rathite may be written as AgxTlyPb16−2(x+y)As16+x+y−zSbzS40 (with 1.6 〈 x 〈 2, 0 〈 y 〈 3, 0 〈 z 〈 3.5). Based on Pb–S bond lengths, polyhedral characteristics and Pb-site bond-valence sums, we conclude that the Pb1 site is more affected by Tl substitution than the Pb2 site. When Tl substitution reaches values above 13 wt% (or 3 apfu), a new phase (“SR”), belonging to the rahite group, appears as lamellar exsolution intergrowths with Tl-rich rathite (11.78 wt%). Rathite is found only in the Lengenbach and Reckibach deposits, Binntal, Canton Wallis, Switzerland.

Description: 〈div data-abstract-type="normal"〉〈p〉Thermodynamic data for the arsenates of various metals are necessary to calculate their solubilities and to evaluate their potential as arsenic storage media. If some of the less common arsenate minerals have been shown to be less soluble than the currently used options for arsenic disposal (especially scorodite and arsenical iron oxides), they should be further investigated as promising storage media. Furthermore, the health risk associated with arsenic minerals is a function of their solubility and bioavailability, not merely their presence. For all these purposes, solubilities of such minerals need to be known. In this work, a complete set of thermodynamic data has been determined for mansfieldite, AlAsO〈span〉4〈/span〉·2H〈span〉2〈/span〉O; angelellite, Fe〈span〉4〈/span〉(AsO〈span〉4〈/span〉)〈span〉2〈/span〉O〈span〉3〈/span〉; and kamarizaite, Fe〈span〉3〈/span〉(AsO〈span〉4〈/span〉)〈span〉2〈/span〉(OH)〈span〉3〈/span〉·3H〈span〉2〈/span〉O, using a combination of high-temperature oxide-melt calorimetry, relaxation calorimetry, solubility measurements, and estimates where possible and appropriate. Several choices for the reference compounds for As for the high-temperature oxide-melt calorimetry were assessed. Scorodite was selected as the best one. The calculated Gibbs free energy of formation (all data in kJ·mol〈span〉–1〈/span〉) is –1733.4 ± 3.5 for mansfieldite, –2319.2 ± 7.9 for angelellite and –3056.8 ± 8.5 for kamarizaite. The solubility products for the dissolution reactions are –21.4 ± 0.5 for mansfieldite, –43.4 ± 1.5 for angelellite and –50.8 ± 1.6 for kamarizaite. Available, but limited, chemical data for the natural scorodite–mansfieldite solid-solution series hint at a miscibility gap; hence the non-ideal nature of the series. However, no mixing parameters were derived because more data are needed. The solubility of mansfieldite is several orders of magnitude higher than that of scorodite. The solubility of kamarizaite, on the other hand, is comparable to that of scorodite, and kamarizaite even has a small stability field in a pH-pε diagram. It is predicted to form under mildly acidic conditions in acid drainage systems that are not subject to rapid neutralization and sudden strong supersaturation. The solubility of angelellite is high, and the mineral is obviously restricted to unusual environments, such as fumaroles. Its crystallization may be enhanced 〈span〉via〈/span〉 its epitaxial relationship with the much more common hematite. The use of the scorodite–mansfieldite solid solution for arsenic disposal, whether the solid solution is ideal or not, is not practical. The difference in solubility products of the two end-members (scorodite and mansfieldite) is so large that almost any system will drive the precipitation of essentially pure scorodite, leaving the aluminium in the aqueous phase.〈/p〉〈/div〉

Description: 〈span〉Lavinskyite-1〈span〉M〈/span〉, a monoclinic MDO (Maximum Degree of Order) polytype related to the orthorhombic MDO polytype lavinskyite-2〈span〉O〈/span〉 (formerly lavinskyite, now redefined), was identified in samples from the Cerchiara manganese mine (Liguria, Italy). Both polytypes have the same ideal chemical formula, K(LiCu)Cu〈sub〉6〈/sub〉(Si〈sub〉4〈/sub〉O〈sub〉11〈/sub〉)〈sub〉2〈/sub〉(OH)〈sub〉4〈/sub〉. Lavinskyite-1〈span〉M〈/span〉 was originally approved as “liguriaite”, but was subsequently redefined as lavinskyite-1〈span〉M〈/span〉 (IMA proposal 16-E).Lavinskyite-1〈span〉M〈/span〉 occurs as blue, micaceous aggregates embedded in calcite-filled microfractures and veinlets, where it is associated with calcite, quartz, norrishite and “schefferite” (a Mn-bearing variety of diopside). Lavinskyite-1〈span〉M〈/span〉 is translucent to transparent, bluish to pale blue in colour with a very pale blue to whitish streak and vitreous lustre; it is non-fluorescent. Individual, always indistinct platelets are up to ∼0.15 mm in length. The crystals are tabular (100) and elongate along [001]. Lavinskyite-1〈span〉M〈/span〉 is brittle with perfect cleavage parallel to {100}, and uneven fracture. The estimated Mohs hardness is ∼5. The calculated density is 3.613 g/cm〈sup〉3〈/sup〉 (for empirical formula). Optically, it is biaxial positive, with α = 1.674(2); β = 1.692(3) and γ = 1.730(3); 2〈span〉V〈/span〉〈sub〉γ〈/sub〉 is very large, ∼75° (est.), 2〈span〉V〈/span〉〈sub〉γ〈/sub〉 (calc.) = 70°. Pleochroism is moderate: 〈span〉X〈/span〉 (pale) blue, 〈span〉Y〈/span〉 pale blue and 〈span〉Z〈/span〉 pale blue with faint greenish tint; absorption 〈span〉X〈/span〉 ≥ 〈span〉Z〈/span〉 ≥ 〈span〉Y〈/span〉. Orientation: 〈span〉X〈/span〉 ^ 〈span〉a〈/span〉 ∼20° (probably in obtuse beta), 〈span〉Y〈/span〉 = 〈span〉b〈/span〉, 〈span〉Z〈/span〉 ∼ 〈span〉c〈/span〉; optical elongation is positive and the optical axis plane is parallel to (010). No dispersion was observed.Chemical analysis (quantitative SEM-EDS and LAICPMS) of two samples yielded the empirical formulae (based on 26 O atoms) (K〈sub〉1.08〈/sub〉)〈sub〉Σ1.08〈/sub〉(Li〈sub〉0.89〈/sub〉Mg〈sub〉0.36〈/sub〉Cu〈sub〉0.33〈/sub〉Na〈sub〉0.22〈/sub〉Mn〈sup〉2+〈/sup〉〈sub〉0.04〈/sub〉)〈sub〉Σ1.86­〈/sub〉Cu〈sub〉6.00〈/sub〉Si〈sub〉8.08〈/sub〉O〈sub〉22〈/sub〉(OH)〈sub〉4〈/sub〉 and (K〈sub〉1.08〈/sub〉)〈sub〉Σ1.08〈/sub〉(Li〈sub〉0.89〈/sub〉Cu〈sub〉0.35〈/sub〉Mg〈sub〉0.28〈/sub〉Na〈sub〉0.22〈/sub〉Mn〈sup〉2+〈/sup〉〈sub〉0.04〈/sub〉) 〈sub〉Σ1.78­〈/sub〉Cu〈sub〉6.00〈/sub〉Si〈sub〉8.12〈/sub〉O〈sub〉22〈/sub〉(OH)〈sub〉4〈/sub〉. Strongest lines in the X-ray powder diffraction pattern are [〈span〉d〈/span〉 in Å (〈span〉I〈/span〉〈sub〉calc〈/sub〉) 〈span〉hkl〈/span〉]): 10.216 (100) 100, 9.007 (20) 110, 4.934 (19) 210, 3.983 (19) 230, 3.353 (33) 310, 2.8693 (22) 241, 2.6155 (35) 161, 2.3719 (23) 20-2. The crystal structure has been solved, using single-crystal X-ray diffractometer data (〈span〉Rint〈/span〉 = 4.60%), by direct methods and refined in space group 〈span〉P〈/span〉2〈sub〉1〈/sub〉/〈span〉c〈/span〉 (no. 14) to 〈span〉R〈/span〉1 = 5.10% and 〈span〉wR〈/span〉2〈sub〉〈span〉all〈/span〉〈/sub〉 = 13.92% [1786 ‘observed’ reflections with 〈span〉F〈/span〉〈sub〉o〈/sub〉 〉 4σ(〈span〉F〈/span〉〈sub〉o〈/sub〉), 199 parameters]. Refined unit-cell parameters are: 〈span〉a〈/span〉 = 10.224(2), 〈span〉b〈/span〉 = 19.085(4), 〈span〉c〈/span〉 = 5.252(1) Å, β = 92.23(3)°, 〈span〉V〈/span〉 = 1024.0(4) Å〈sup〉3〈/sup〉 (〈span〉Z〈/span〉 = 2). The chemical composition and crystal structure are supported by micro-Raman spectra.Lavinskyite-1〈span〉M〈/span〉 has a sheet structure consisting of corrugated brucite-like (CuO〈sub〉2〈/sub〉)〈sub〉n〈/sub〉 layers with amphibole-type (SiO〈sub〉3〈/sub〉)〈sub〉n〈/sub〉 chains joined to both their upper and lower surfaces. Adjacent complex sheets are linked by [5]-coordinated Li atoms and Cu atoms in square coordination (nearly planar) and interlayer K atoms. Lavinskyite-1〈span〉M〈/span〉 is isostructural with a hypothetical monoclinic MDO polytype of plancheite, not yet found in nature, while lavinskyite-2〈span〉O〈/span〉 is isostructural with plancheite. It appears that a complex and delicate interplay between the Li:Cu and Cu:Mg ratios (lower in lavinskyite-1〈span〉M〈/span〉), along with an additional influence of impurity cations such as Na and different conditions of formation, results in a stabilisation of the 1〈span〉M〈/span〉 polytype. The origin of lavinskyite-1〈span〉M〈/span〉 can be related to a complex, multi-stage hydrothermal evolution of the primary Fe-Mn ore at Cerchiara, which experienced a diffuse alkali metasomatism under strongly oxidising conditions and produced mineral assemblages enriched in Na, K and Li, while providing also appreciable amounts of Ba, Sr, Ca and Cu.〈/span〉

Description: 〈span〉Vanderheydenite, Zn〈sub〉6〈/sub〉(PO〈sub〉4〈/sub〉)〈sub〉2〈/sub〉(SO〈sub〉4〈/sub〉)(OH)〈sub〉4〈/sub〉·7H〈sub〉2〈/sub〉O, is a new mineral from the Block 14 Opencut, Broken Hill, New South Wales, Australia. It occurs as aggregates of colourless crystals up to 0.5 mm across in voids of a sphalerite–galena matrix and is associated with anglesite, pyromorphite, sulfur, and liversidgeite. Crystals are pseudohexagonal blades up to 0.4 mm in length, flattened on {1 0 0} and exhibiting the forms {1 0 0}, {0 1 0}, and {0 2 1}. Cleavage was not observed. The Mohs hardness is estimated to be 3. The calculated density is 3.12 g/cm〈sup〉3〈/sup〉 from the empirical formula and 3.06 g/cm〈sup〉3〈/sup〉 from the ideal formula. The mineral is optically biaxial (–), with α = 1.565(4), β = 1.580(4) and γ = 1.582(4). The calculated 2〈span〉V〈/span〉 is 39.8°. Chemical analysis by electron microprobe gave ZnO 55.63, CuO 0.07, FeO 0.11, MnO 0.06, P〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 14.18, As〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 4.33, SO〈sub〉3〈/sub〉 8.71, H〈sub〉2〈/sub〉O 18.31, total 101.40 wt%, with H〈sub〉2〈/sub〉O content derived from the refined crystal structure. The empirical formula calculated on the basis of 23 oxygen atoms is (Zn〈sub〉5.99〈/sub〉Cu〈sub〉0.01〈/sub〉Fe〈sub〉0.01〈/sub〉Mn〈sub〉0.01〈/sub〉)〈sub〉Σ6.02〈/sub〉[(PO〈sub〉4〈/sub〉)〈sub〉1.75〈/sub〉(AsO〈sub〉4〈/sub〉)〈sub〉0.33〈/sub〉]〈sub〉Σ2.08〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉0.95〈/sub〉(OH)〈sub〉3.91〈/sub〉·6.96H〈sub〉2〈/sub〉O. The mineral is monoclinic, 〈span〉P〈/span〉2〈sub〉1〈/sub〉/〈span〉n〈/span〉, with 〈span〉a〈/span〉 = 6.2040(12), 〈span〉b〈/span〉 = 19.619(4), 〈span〉c〈/span〉 = 7.7821(16) Å, β = 90.67(3)°, 〈span〉V〈/span〉 = 947.1(3) Å〈sup〉3〈/sup〉. The five strongest lines in the X-ray powder diffraction pattern are [〈span〉d〈/span〉(Å), (〈span〉I〈/span〉), (〈span〉hkl〈/span〉)]: 9.826 (57) (0 2 0), 7.296 (20) (0 1 1), 6.134 (1 0 0) (0 2 1), 3.368 (10) (0 3 2, 1 5 0), 3.069 (9) (2 1 0, 0 4 2). The crystal structure of vanderheydenite (〈span〉R〈/span〉1 = 0.0497 for 939 reflections with 〈span〉F〈/span〉〈sub〉o 〈/sub〉〉 4σ〈span〉F〈/span〉) contains chains of edge-sharing ZnO〈sub〉6〈/sub〉 octahedra parallel to 〈span〉a〈/span〉 that are linked by edge- and corner-sharing ZnO〈sub〉5〈/sub〉 trigonal bipyramids and 〈span〉T〈/span〉O〈sub〉4〈/sub〉 (〈span〉T〈/span〉 = P, As) tetrahedra forming zig-zag sheets parallel to {0 1 0}. Sheets are linked by half-occupied, distorted 〈span〉T〈/span〉O〈sub〉4〈/sub〉 (〈span〉T〈/span〉 = P, S) tetrahedra in the [0 1 1] direction. Interstitial channels extend parallel to the 〈span〉a〈/span〉-direction and are occupied by strongly to weakly hydrogen-bonded H〈sub〉2〈/sub〉O groups.〈/span〉