福島県塙町長久木産 Joseite-A

概要

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Average of three microprobe analyses of joseite A in diopside-grossular-quartz skarn from Nagakukiis : Bi 82.16,Pb 0.22,Te 10.56,S 6.52,Se 0.10,total 99.56%. The empirical formula calculated on the basis of total atoms=7 is (Bi_<4.04>Pb_<0.01>)_<Σ4.05> (Te_<0.85>S_<0.09>Se_<0.01>)_<Σ0.95>S_<2.00>, which is placed between the ideal formulae of joseite-A (Bi_4TeS_2) and joseite-C (Bi_<16>Te_3S_9), the natures of the latter being considered. The associated opaque minerals include native bismuth, bismuthinite, pyrrhotite, chalcopyrite, sphalerite, and minor native gold. The mineralogical implication of the association of three bismuth minerals is presented. The mineralogical differences between joseite-A and joseite-B are considered. The ideal formula of the latter, Bi_4Te_2S, is given as 2 Bi+Bi_2Te_2S (tetradymite), while the former has no mineral corresponding to tetradymite, though csiklovaite is to have the chemical formula Bi_2Te(S, Se)_2 where S> Se. The status of this mineral is also considered to conclude that the existence as a bismuth chalcogenide seems unlikely, unless any other constituent than bismuth and chalcogenides such as lead or silver partakes as the essential consitituent.
1994-12-22