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

Published online by Cambridge University Press:  05 July 2018

I. Kusachi ,
C. Henmi  and
S. Kobayashi
I. Kusachi
Affiliation:
Department of Earth Sciences, Faculty of Education, Okayama University, Okayama 700, Japan
C. Henmi
Affiliation:
Department of Earth Sciences, Faculty of Science, Okayama University, Okayama 700, Japan
S. Kobayashi
Affiliation:
Department of Earth Sciences, Faculty of Science, Okayama University of Science, Okayama 700, Japan
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Abstract

Takedaite, Ca3B2O6, has been found in crystalline limestone near gehlenite−spurrite skarns at Fuka, Okayama Prefecture. It occurs as aggregates of granular crystals up to 0.8 mm long and 0.3 mm wide. The mineral is associated with nifontovite, olshanskyite, pentahydroborite, frolovite, sibirskite, calcite and an unidentified mineral, is white or pale gray, and has a vitreous luster. Takedaite is trigonal with space group of Rc, a = 8.638(1), c = 11.850(2)Å, Z = 6. The strongest lines in the X-ray powder pattern [d in A(I)(hkl)] are 2.915(100)(113), 1.895(75)(223), 2.756(61)(104), 2.493(44)(300), 2.044(21) (214,131), 2.160(19)(220), 1.976(18)(006), 1.549(12)(306). The Vickers microhardness is 478 kg mm−2 and the Mohs hardness 4.5. The density is 3.10(2) g cm−3 (meas.) and 3.11 g cm−3 (calc.). Wet chemical analyses give the values CaO 71.13%, B2O3 28.41%, ig. loss 0.14%, and total 99.68%. The empirical formula calculated on the basis of O = 6 is Ca3.053B1.965O6, with the simplified formula of Ca3B2O6.

Keywords

takedaitenew mineralborateFukaJapan
Type
Mineralogy
Information
Mineralogical Magazine , Volume 59 , Issue 396 , September 1995 , pp. 549 - 552
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1995

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