Aklimaite, Ca-4[Si2O5(OH)(2)](OH)(4) center dot 5H(2)O, a new natural hydrosilicate from Mount Lakargi, the Northern Caucasus, Russia

作者：Zadov A E; Pekov I V; Zubkova N V; Gazeev V M; Chukanov N V; Yapaskurt V O; Kartasheov P M; Galuskin E V; Galuskina I O; Pertsev N N; Gurbanov A G; Pushcharovsky D Yu

来源：Geology of Ore Deposits, 2013, 55(7): 541-548.

DOI：10.1134/S1075701513070131

A new mineral aklimaite, Ca-4[Si2O5(OH)(2)](OH)(4) center dot 5H(2)O, 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 x 0.1 x 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%26apos; hardness is 3-4. Aklimaite is optically biaxial, negative, 2V (meas) %26gt; 70A degrees, 2V (calc) = 78A degrees, alpha = 1.548(2), beta = 1.551(3), gamma = 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=F-2; the total is 99.03. The empirical formula calculated on the basis of 2Si apfu with O + OH + F = 16 is as follows: (Ca4.02Na0.01)(I 4.03)[Si2.00O5.07(OH)(1.93)][(OH)(3.16)F-0.84] pound (I 4.00) pound center dot 5H(2)O. The mineral is monoclinic, space group C2/m, a = 16.907(5), b = 3.6528(8), c = 13.068(4) , beta = 117.25(4)center dot, V= 717.5(4) (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, (hkl)] are: 11.64(100)(001), 2.948(32)(310, 203), 3.073(20) (, ), 2.320(12)(005, 510), 2.901 (11)(004), 8.30(10). The type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

• 出版日期2013-12