Acicular crystal of barite was found in epithermal vein embedded in Tertiary shale and tuff at Kominato mine, Aomori Prefecture. The mineral associates with pyrite, chalcedony and quartz. The sequence of mineralization is expressed as barite-pyrite-chalcedony-quartz. The crystal of barite elongates parallel to a-axis and its dominant face is o (011). Refractive indices are α=1.636, γ=1.647 and specific gravity is 4.300. The result of chemical analysis is as shown in Table 1 and its chemical formula is given as (Ba
0.97 Ca
0.02)
0.99 S
1.00 O4.00 Under the mineralight, the mineral shows strong yellow fluorescence.
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