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A barian bannisterite from Japan

Published online by Cambridge University Press:  05 July 2018

S. Matsubara
Affiliation:
Department of Geology, National Science Museum, 3-23-1 Hyakunin-cho, Shinjuku, Tokyo 169, Japan
A. Kato
Affiliation:
Department of Geology, National Science Museum, 3-23-1 Hyakunin-cho, Shinjuku, Tokyo 169, Japan

Abstract

Chemical analyses of bannisterite from the Kamo mine, Toba City, Mie Prefecture, Japan, give Ba : Ca = 69:31–55:45, yielding the ideal formula with Ba > Ca, i.e. (Ba,Ca)(K,H3O)(Mn2+ · Mg,Fe2+)21 (Si,Al)32(O,OH)92 · nH2O, where Ba > Ca, Mn2+ > Mg, Fe2+,Si ≫ Al, and O > OH. The unit cell parameters calculated after the indexing of the X-ray powder pattern are: a = 22.95, b = 16.52, c = 25.66 Å, β = 94.2°. It occurs as dark brown veinlets cutting massive caryopilite-rhodochrosite ore, which is also cut by veinlets of manganoan chlorite (Mn/(Mg + Mn + Fe) = c. 0.30–0.39) with minor barian orthoclase (Ba/(K+ Ba) = 0.05 ∼ 0.06).

Type
Mineralogy
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1989

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References

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