Hilarionite, Fe3+2(SO4)(AsO4)(OH)•6H2O, a new hypergene mineral from Lavrion, Greeceстатья
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Аннотация:A new mineral, hilarionite, ideally (SO4)(AsO4)(OH) ⋅ 6H2O, has been found in the Hilar
ion Mine, Agios Konstantinos, Kamariza, Lavrion district, Attiki Prefecture, Greece. It was formed in the oxidation zone of a sulfiderich orebody in association with goethite, gypsum, bukovskyite, jarosite, melanterite, chalcanthite, allophane, and azurite. Hilarionite occurs as light green (typically with an olive or grayishtint) to light yellowish green spherulites (up to 1 mm in size) and bunches of prismatic to acicular “individu
als” up to 0.5 mm long that are in fact nearparallel or divergent aggregates of very thin, curved fibers up to 0.3 mm long and usually lesser than 2 μm thick. The luster is silky to vitreous. The Mohs’ hardness is ca. 2. Hilarionite is ductile, its “individuals” are flexible and inelastic; fracture is uneven or splintery. D(meas) = 2.40(5), D(calc) = 2.486 g/cm3. IR spectrum shows the presence of arsenate and sulfate groups and H2O molecules in significant amounts. The Mössbauer spectrum indicates the presence of Fe3+ at two sixfold coordinated sites and the absence of Fe2+. Hilarionite is optically biaxial (+), α = 1.575(2), γ = 1.64(2), 2V is large. The chemical composition (electron microprobe, average of 7 point analyses; H2O determined by modified Penfield method) is as follows, wt %: 0.03 MnO, 0.18 CuO, 0.17 ZnO, 33.83 Fe2O3, 0.22 P2O5, 18.92 As2O5,22.19 SO3, 26.3 H2O, total is 101.82%. The empirical formula calculated on the basis of 15 O is:
Cu0.01Zn0.01)Σ1.92[(SO4)1.24(AsO4)0.74(PO4)0.01]Σ1.99(OH)1.01 ⋅ 6.03H2O. The Xray powder diffraction data show close structural relationship of hilarionite and ka kite, (AsO4)2 ⋅ 7H2O. Hilarionite is mono clinic, space group C2/m, Cm or C2, a = 18.53(4), b = 17.43(3), c = 7.56(1) Å, β = 94.06(15)°, V = 2436(3) Å3,Z = 8. The strongest reflections in the Xray powder diffraction pattern (d, Å–I[hkl]) are: 12.66–100[110],7.60–6[001], 5.00–10[22l], 4.70–10[311], 4.33–7[040]. Hilarionite is named after its type locality.