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A barian bannisterite from Japan

1989; Cambridge University Press; Volume: 53; Issue: 369 Linguagem: Inglês

10.1180/minmag.1989.053.369.09

1471-8022

S. Matsubara, A. Kato,

Polyoxometalates: Synthesis and Applications

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,H 3 O)(Mn 2+ · Mg,Fe 2+ ) 21 (Si,Al) 32 (O,OH) 92 · n H 2 O, where Ba > Ca, Mn 2+ > Mg, Fe 2+ ,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).