ALBERT

Description: The new mineral reynoldsite, Pb2Mn4+2O5(CrO4), occurs at the Blue Bell claims, near Baker, San Bernardino County, California, U.S.A., and at the Red Lead mine, Dundas, Tasmania, Australia. At the Blue Bell claims, reynoldsite occurs in subparallel growths and divergent sprays of thin prisms with a square cross section. At the Red Lead mine, it occurs as thin rectangular blades. At both occurrences, crystals are small (≤0.2 mm), and ubiquitously and multiply twinned. At both deposits, reynoldsite formed as a secondary mineral derived from the weathering of primary minerals including oxides and sulfides in the presence of acidic groundwater. Reynoldsite is dark orange-brown to black in color and has a dark orange-brown streak. Its luster is subadamantine and its Mohs hardness is about 4½. The mineral is brittle with irregular to splintery fracture and a poorly developed {001} cleavage. The calculated density is 6.574 g/cm3 (Red Lead mine). The very high indices of refraction and dark color permitted only partial determination of the transmitted light optical properties. Electron microprobe analyses of Blue Bell and Red Lead reynoldsite provided the empirical formulas (based on nine O atoms): Pb1.97Mn2.01O5(Cr1.01O4) and (Pb2.07Sr0.04)∑2.11Mn2.15O5(Cr0.87O4), respectively. The strongest powder X-ray diffraction lines for Red Lead reynoldsite are [d(hkl)I]: 3.427(02̄1,110)52, 3.254(021,11̄2,12̄1)85, 3.052(1̄1̄2,111,02̄2,1̄03)100, 2.923(013,1̄22)40, 2.5015(004,2̄11,1̄30)47, 1.9818(01̄5,1̄05,202,23̄1)42, 1.7694(11̄5,13̄4,203,1̄42,1̄3̄3)36, and 1.6368(2̄2̄3,04̄3,221,124,22̄4)36. Reynoldsite is triclinic with space group P1̄ and unit-cell parameters: a = 5.0278(7), b = 7.5865(11), c = 10.2808(15) Å, α = 91.968(12), β = 99.405(12), γ = 109.159(10)°, V = 363.81(9) Å3, and Z = 2 (for a Red Lead mine crystal). The crystal structure of reynoldsite (R1 = 10.2% for 902 reflections with Fo 〉 4σF for a Red Lead crystal) contains close-packed layers of edge-sharing Mn4+O6 octahedra parallel to {001}. These layers are composed of edge-sharing double chains of octahedra extending along [100], which in turn are linked to one another by sharing edges in the [010] direction. The thick interlayer region contains Pb2+ cations and CrO4 tetrahedra. The 6s2 lone-electron pair of the Pb2+ is stereochemically active, resulting in a one-sided Pb-O coordination arrangement. The structure bears strong similarities to those of the phyllomanganates, such as chalcophanite and birnessite.

Description: The new mineral fluorphosphohedyphane, Ca2Pb3(PO4)3F, the F-analog of phosphohedyphane, is hexagonal with space group P63/m and cell parameters a = 9.6402(12), c = 7.0121(8) A, V = 564.4(1) A3, and Z = 2. It occurs in the oxidation zone of a small Pb-Cu-Zn-Ag deposit, the Blue Bell claims, about 11 km west of Baker, San Bernardino County, California. It forms as sub-parallel intergrowths and irregular clusters of transparent, colorless, highly lustrous, hexagonal prisms with pyramidal terminations. It is found in cracks and narrow veins in a highly siliceous hornfels in association with cerussite, chrysocolla, fluorite, fluorapatite, goethite, gypsum, mimetite, opal, phosphohedyphane, plumbogummite, plumbophyllite, plumbotsumite, pyromorphite, quartz, and wulfenite. The streak of the new mineral is white, the luster is subadamantine, and the Mohs hardness is about 4. The mineral is brittle with subconcoidal fracture and no cleavage. The calculated density is 5.445 g/cm3 based upon the empirical formula. Optical properties (589 nm): uniaxial (-), {omega} = 1.836(5), {varepsilon} = 1.824(5), nonpleochroic. SEM-EDS analyses yielded the averages and ranges in wt%: O 21.28 (20.31-22.14), F 1.59 (1.38-1.91), P 10.33 (9.81-10.83), Ca 9.66 (8.97-10.67), Pb 60.08 (57.67-61.21), total 102.95 (102.02-103.88), providing the empirical formula (based on P = 3): Ca2.00(Pb2.61Ca0.17){sum}2.78P3O11.91F0.75. Infrared spectroscopy showed no evidence of OH or carbonate. The strongest powder X-ray diffraction lines are [d(hkl)I]: 8.38(100)22, 3.974(111)28, 3.506(002)25, 2.877(121,211)100, 1.878(213,123)26. Fluorphosphohedyphane has the apatite structure (R1 = 1.75% for 444 reflections with Fo 〉 4{sigma}F) with ordering of Ca and Pb in two cation sites, as in hedyphane and phosphohedyphane. The Pb2+ cation exhibits a stereoactive 6s2 lone-electron-pair. The X anion site at (0, 0,[1/2]) is fully occupied by F forming six bonds of 2.867 A to Pb atoms, in contrast to the six Pb-Cl bonds of 3.068 A in phosphohedyphane.

Description: Chromschieffelinite, Pb10Te6O20(OH)14(CrO4)(H2O)5, is a new tellurate from Otto Mountain near Baker, California, named as the chromate analog of schieffelinite, Pb10Te6O20(OH)14(SO4)(H2O)5. The new mineral occurs in a single 1 mm vug in a quartz vein. Associated mineral species include: chalcopyrite, chrysocolla, galena, goethite, hematite, khinite, pyrite, and wulfenite. Chromschieffelinite is orthorhombic, space group C2221, a = 9.6646(3), b = 19.4962(8), c = 10.5101(7) Å, V = 1980.33(17) Å3, and Z = 2. Crystals are blocky to tabular on {010} with striations parallel to [001]. The forms observed are {010}, {210}, {120}, {150}, {180}, {212}, and {101}, and crystals reach 0.2 mm in maximum dimension. The color and streak are pale yellow and the luster is adamantine. The Mohs hardness is estimated at 2. The new mineral is brittle with irregular fracture and one perfect cleavage on {010}. The calculated density based on the ideal formula is 5.892 g/cm3. Chromschieffelinite is biaxial (-) with indices of refraction a = 1.930(5), ß = 1.960(5), and ? = 1.975(5), measured in white light. The measured 2V is 68(2)°, the dispersion is strong, r 〈 v, and the optical orientation is X = b, Y = c, Z = a. No pleochroism was observed. Electron microprobe analysis provided: PbO 59.42, TeO3 29.08, CrO3 1.86, H2O 6.63 (structure), total 96.99 wt%; the empirical formula (based on 6 Te) is Pb9.65Te6O19.96(OH)14.04(CrO4)0.67(H2O)6.32. The strongest powder X-ray diffraction lines are [dobs in Å (hkl) I]: 9.814 (020) 100, 3.575 (042,202) 41, 3.347 (222) 44, 3.262 (241,060,113) 53, 3.052 (311) 45, 2.9455 (152,133) 55, 2.0396 (115,353) 33, and 1.6500 (multiple) 33. The crystal structures of schieffelinite (R1 = 0.0282) and chromschieffelinite (R1 = 0.0277) contain isolated Te6+O6 octahedra and Te26+O11 corner-sharing dimers, which are linked into a three-dimensional framework via bonds to Pb2+ atoms. The framework has large channels along c, which contain disordered SO4 or CrO4 groups and H2O. The lone-electron pair of each Pb2+ is stereochemically active, resulting in one-sided Pb-O coordination arrangements. The short Pb-O bonds of the Pb2+ coordinations are all to Te6+O6 octahedra, resulting in strongly bonded layers parallel to {010}, which accounts for the perfect {010} cleavage.

Description: Hagstromite, Pb8Cu2+(Te6+O6)2(CO3)Cl4, (IMA2019-093) is a new tellurate mineral from Otto Mountain near Baker, California, USA. It occurs on quartz in association with cerussite, fuettererite and thorneite. It is a secondary oxidation zone mineral and is presumed to have formed by oxidation of earlier formed tellurides, chalcopyrite and galena. Hagstromite occurs as light yellow–green blades, up to ~100 μm long. Crystals are transparent with adamantine to silky lustre. The mineral is brittle with two cleavages providing splintery fracture; the Mohs hardness is probably between 2 and 3. The calculated density is 7.062 g cm–3. Hagstromite is optically biaxial (+), with calculated indices of refraction for α = 2.045, β = 2.066 and γ = 2.102; 2Vmeas = 76(1)°; and optical orientation X = b, Y = a and Z = c. The Raman spectrum of hagstromite exhibits similarities with those of agaite and thorneite and confirms the presence of CO32–. The electron microprobe analyses provided the empirical formula Pb8.07Cu2+0.98Te6+1.96C1.17Cl3.83O15.34. Hagstromite is orthorhombic, space group Ibam, with a = 23.688(17), b = 9.026(8), c = 10.461(8) Å, V = 2237(3) Å3 and Z = 4. The crystal structure of hagstromite (R1 = 0.0659 for 284 I 〉 2σI reflections) contains a novel Cu2+Te6+2O12 chain assembled of corner-sharing Cu2+O4 squares and Te6+O6 octahedra. The O atoms in the chains form bonds with Pb2+ cations, which in turn bond to Cl– and CO32– anions, thereby creating a framework structure.

Description: 〈div data-abstract-type="normal"〉〈p〉The crystal structure of tlapallite has been determined using single-crystal X-ray diffraction and supported by electron probe micro-analysis, powder diffraction and Raman spectroscopy. Tlapallite is trigonal, space group 〈span〉P〈/span〉321, with 〈span〉a〈/span〉 = 9.1219(17) Å, 〈span〉c〈/span〉 = 11.9320(9) Å and 〈span〉V〈/span〉 = 859.8(3) Å〈span〉3〈/span〉, and was refined to 〈span〉R〈/span〉〈span〉1〈/span〉 = 0.0296 for 786 reflections with 〈span〉I〈/span〉 〉 2σ(〈span〉I〈/span〉). This study resulted from the discovery of well-crystallised tlapallite at the Wildcat prospect, Utah, USA. The chemical formula of tlapallite has been revised to (Ca,Pb)〈span〉3〈/span〉CaCu〈span〉6〈/span〉[Te〈span〉4+〈/span〉〈span〉3〈/span〉Te〈span〉6+〈/span〉O〈span〉12〈/span〉]〈span〉2〈/span〉(Te〈span〉4+〈/span〉O〈span〉3〈/span〉)〈span〉2〈/span〉(SO〈span〉4〈/span〉)〈span〉2〈/span〉·3H〈span〉2〈/span〉O, or more simply (Ca,Pb)〈span〉3〈/span〉CaCu〈span〉6〈/span〉Te〈span〉4+〈/span〉〈span〉8〈/span〉Te〈span〉6+〈/span〉〈span〉2〈/span〉O〈span〉30〈/span〉(SO〈span〉4〈/span〉)〈span〉2〈/span〉·3H〈span〉2〈/span〉O, from H〈span〉6〈/span〉(Ca,Pb)〈span〉2〈/span〉(Cu,Zn)〈span〉3〈/span〉(TeO〈span〉3〈/span〉)〈span〉4〈/span〉(TeO〈span〉6〈/span〉)(SO〈span〉4〈/span〉). The tlapallite structure consists of layers containing distorted Cu〈span〉2+〈/span〉O〈span〉6〈/span〉 octahedra, Te〈span〉6+〈/span〉O〈span〉6〈/span〉 octahedra and Te〈span〉4+〈/span〉O〈span〉4〈/span〉 disphenoids (which together form the new mixed-valence phyllotellurate anion [Te〈span〉4+〈/span〉〈span〉3〈/span〉Te〈span〉6+〈/span〉O〈span〉12〈/span〉]〈span〉12−〈/span〉), Te〈span〉4+〈/span〉O〈span〉3〈/span〉 trigonal pyramids and CaO〈span〉8〈/span〉 polyhedra. SO〈span〉4〈/span〉 tetrahedra, Ca(H〈span〉2〈/span〉O)〈span〉3〈/span〉O〈span〉6〈/span〉 polyhedra and H〈span〉2〈/span〉O groups fill the space between the layers. Tlapallite is only the second naturally occurring compound containing tellurium in both the 4〈span〉+〈/span〉 and 6〈span〉+〈/span〉 oxidation states with a known crystal structure, the other being carlfriesite, CaTe〈span〉4+〈/span〉〈span〉2〈/span〉Te〈span〉6+〈/span〉O〈span〉8〈/span〉. Carlfriesite is the predominant secondary tellurium mineral at the Wildcat prospect. We also present an updated structure for carlfriesite, which has been refined to 〈span〉R〈/span〉〈span〉1〈/span〉 = 0.0230 for 874 reflections with 〈span〉I〈/span〉 〉 2σ(〈span〉I〈/span〉). This updated structural refinement improves upon the one reported previously by refining all atoms anisotropically and presenting models of bond valence and Te〈span〉4+〈/span〉 secondary bonding.〈/p〉〈/div〉