Parasibirskite, a new mineral from Fuka, Okayama Prefecture, Japan

Authors: Kusachi I.¹; Takechi Y.¹; Henmi C.²; Kobayashi S.³

Source: Mineralogical Magazine, Volume 62, Number 4, 1 August 1998 , pp. 521-525(5)

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Abstract:

Parasibirskite, with the ideal formula Ca₂B₂O₅.H₂O, is a new mineral species found at Fuka, Okayama Prefecture, Japan. It is a polymorph of sibirskite, CaHBO₃, and occurs as subparallel aggregates of tabular crystals up to 40x20x3

m in size. Associated minerals are takedaite, olshanskyite, sibirskite, frolovite and calcite. The mineral is white, and has a weak pearly luster. Optically, the mineral is biaxial positive, alpha

1.556(2),

1.593(2),

1.663(2) ( lambda

589 nm). The Vickers microhardness of aggregates is 121 kg mm-2. The mineral is monoclinic with space group of P2₁/m, a 6.722(4), b 5.437(2), c 3.555(2) Å, beta

93.00(5)°, V 129.8(2) Å³. The strongest lines in the X-ray powder pattern (d in Å (I)(hkl)) are 2.237(100)(300), 6.73(70)(100), 2.975(60)(011), 3.354(30)(200), 2.855(20)(210) and 1.776(20) (002). Wet chemical analysis, electron-microprobe analysis and ICP emission spectrometry give the values CaO 56.06 %, B₂O₃ 34.10 %, H₂O 9.97 % and total 100.13%. The empirical formula calculated on the basis of O = 6 is Ca_1.985B_1.945O_4.901 1.099H₂O, for Z = 1, D_calc 2.54 and D_meas 2.50(1) g cm^-3. Parasibirskite is formed by hydrothermal alteration of takedaite.

Keywords: PARASIBIRSKITE; SIBIRSKITE; GEHLENITE-SPURRITE; SKARNS; BORATE; FUKA; JAPAN

Language: English

Document Type: Research article

Affiliations: 1: Department of Earth Sciences, Faculty of Education, Okayama University, Okayama, 700-8530, Japan 2: Department of Earth Sciences, Faculty of Science, Okayama University, Okayama, 700-8530, Japan 3: Division of Earth Sciences, Kurashiki University of Science and the Arts, Kurashiki, 712-8505, Japan

Publication date: 1998-08-01

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Parasibirskite, a new mineral from Fuka, Okayama Prefecture, Japan

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