Teallite from the Toyoha mine, Hokkaido

Abstract

Teallite was firstly found in Japan from a new vein (Sorachi uwaban-hi) of the Toyoha mine, Hokkaido. It occurs in association with galena and sometimes sphalerite in central drusy portion of zinc and lead veinlet, 0.5 to 1.0cm in width, which cuts principal pyrite ore containing sphalerite, arsenopyrite, quartz and small amounts of cassiterite and stannite in the vein. Teallite appears as aggregate of curved thin-platy or flaky crystals, 0.5 to 5.0mm in length and 1 to 20μm in thickness, and shows metallic ruster of silver white in color. Under ore microscope, it has distinct pleochroism from yellowish white to pale brownish white, and strong anisotropism from brownish gray to bluish brown. It changes to black immediately by HNO3 (1:1), and reacts slightly with FeCl3 (20%) to stain pale brown. No etching reaction with HCl(1:1), HgCl2 (sat.), KCN (20%) and KOH (sat.) was observed. The reflectances measured at 406, 436, 497, 546, 586 and 648nm in wave length are: 34.3-50.0, 31.5-50.7, 32.1-50.2, 34.7-49.7, 35.2-48.6, 34.5-49.5%, respectively. Vickers hardness (10g load) on {010} is 10.8-19.3kg/mm2. Its cell dimension is orthorhombic, a=4.258 (1), b=11.447 (3), c=4.103 (1)A. Chemical compositions of teallite obtained by EPMA are Pb1.07-1.10Cu0.02-0.04Fe0.01-0.02Zn0.02-0.08Sn0.84-0.87S1.95-2.02 on the basis of 4 atoms per molecule. They are plotted in PbS side of PbSnS2 in the PbS-SnS join, although all the compositions of teallite reported by authors up to now are in the SnS side of the join.