Aklimaite, Ca4[Si2O5(OH)_2](OH)_4 ? 5H2O, A New Natural Hydrosilicate from Mount Lakargi, the Northern Caucasus, Russia
  • 【摘要】

    A new mineral aklimaite, Ca4[Si2O5(OH)_2](OH)_4 ? 5H2O, has been found near Mount Lakargi, Upper Chegem caldera, Kabardino-Balkaria, the Northern Caucasus, Russia, in the skarnified limestone xenolith... 展开>>A new mineral aklimaite, Ca4[Si2O5(OH)_2](OH)_4 ? 5H2O, has been found near Mount Lakargi, Upper Chegem caldera, Kabardino-Balkaria, the Northern Caucasus, Russia, in the skarnified limestone xenolith in ignimbrite. This hydrothermal mineral occurs in a cavity of altered larnite skarn and is associated with larnite, calcium humite-group members, hydrogarnets, bultfonteinite, afwillite, and ettringite. Aklimaite forms transparent, colorless (or occasionally with pinkish tint) columnar or lath-shaped crystals up 3 × 0.1 × 0.01 mm in size, flattened on {001} and elongated along {010}; they are combined in spherulites. The luster is vitreous; the cleavage parallel to the {001} is perfect. D_(calc) = 2.274 g/cm~3. The Mohs' hardness is 3— 4. Aklimaite is optically biaxial, negative, 2V_(meas) > 70°, 2V_(calc)= 78°, α = 1.548(2), β = 1.551(3), γ = 1.553(2). The IR and Raman spectra are given. The chemical composition (wt %, electron microprobe) is as follows: 0.06 Na2O, 0.02 K2O, 45.39 CaO, 0.01 MnO, 0.02 FeO, 24.23 SiO2, 0.04 SO3, 3.22 F, 27.40 H2O_((calc.)), -1.36 -O=F2; the total is 99.03. The empirical formula calculated on the basis of 2Si apfu with O + OH + F = 16 is as follows: (Ca_(4.02)Na_(0.01))_(Σ4.03)[Si_(2.00)O_(5.07)(OH)_(1.93)][(OH)_(316)F_(0.84)]_(Σ4.00) ? 5H2O. The mineral is monoclinic, space group C2/m, a = 16.907(5), b = 3.6528(8), c = 13.068(4) A, β = 117.25(4)°, V= 717.5(4) A~3, Z= 2. Aklimaite is representative of the new structural type, the sorosilicate with disilicate groups [Si2O5(OH)_2]. The strongest reflections in the X-ray powder patterns [d, A (hkl)] are: 11.64(100)(001), 2.948(32)(310, 203), 3.073(20) (404, 311 ),2.320(12)(005, 510), 2.901 (11)(004),8.30(10)(201). The type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow. 收起<<

  • 【作者】

    A. E. Zadov  I. V. Pekov  N. V. Zubkova 

  • 【刊期】

    Geology of Ore Deposits EI SCI 2013年7期

  • 【语种】

    eng