Abstract
Ikunolite, Bi4(S, Se)3, a new mineral from the Ikuno mine occurs in ferberite-bismuth-bismuthinite quartz vein. It belongs to rhombohedral system with arh=13.28Å, ?? =18°00′, Z=1 (or a0=4.15Å, c0=39.19Å, Z=3 in hexagonal lattice) and the space group is R ?? 3m. Physical and optical properties are: lead grey in colour and dark grey in streak colour; hardness 2, very flexible; specific gravity=7.97 (calc.), 7.8 (meas.); perfect cleavage parallel to {0001}; anisotropic in the section diagonal to the basal cleavage and etched by HNO3 and FeCl3 solution. Chemical analysis gives Bi3•79 (S2•76Se0•24)3.00 close to Bi4 (S, Se)3 with S:Se=92:8. The sheet structure determined by single crystal method is closely related to the other rhombohedral chalcogenides of bismuth. Ikunolite resembles joseite A [Bi4TeS2] in structure, crystallography and optical properties and belongs to the same group of bismuth-chalcogenide minerals with Bi:(S, Se, Te)=4:3.
