Uralborite from Fuka, Okayama Prefecture, Japan.
| Accession number;00A0735608 |
| Title;Uralborite from Fuka, Okayama Prefecture, Japan. |
| Author;KUSACHI I(Okayama Univ., Okayama, Jpn) SHIRAGA K(Okayama Univ., Okayama, Jpn) KOBAYASHI S(Kurashiki Univ. Sci. And Arts, Kurashiki, Jpn) YAMAKAWA J(Okayama Univ., Okayama, Jpn) TAKEUCHI Y(Kurashiki Museum Of Natural History, Kurashiki, Jpn) |
Journal Title;J Mineral Petrol Sci
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Journal Code:G0150B
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ISSN:1345-6296
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VOL.95;NO.4;PAGE.43-47(2000)
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| Figure&Table&Reference;FIG.6, TBL.3, REF.11 |
| Pub. Country;Japan |
| Language;English |
| Abstract;Uralborite, CaB2O2(OH)4, was found in a vein consisting of borate minerals that cut into crystalline limestone at Fuka, Okayama Prefecture, Japan. It occurs as aggregates of fibrous crystals up to 0.2mm long and as euhedral crystals up to 7mm long and 3mm wide, in association with sibirskite, borcarite, fluorite and calcite, Electron microprobe analyses and ICP gave the empirical formula Ca1.006B2.019O2.069(OH)3.931 on the basis of O=6. X-ray powder diffraction were indexed on the monoclinic cell, a=6.923(1), b=12.326(1), c=9.831(1).ANGS., .BETA.=97.09(1).DEG., determined by a single crystal method. The mineral was optically biaxial positive with refractive indices .ALPHA.=1.605(2), .BETA.=1.611(2), .GAMMA.=1.618(2). The Vickers microhardness was 372kg mm-2 and the Moh's scale of hardness was 4.5. The density was 2.58(2) g cm-1. It is likely that uralborite at Fuka was formed as a secondary mineral by a late-hydrothermal alteration of sibirskite. (author abst.) |
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