Abstract
Fujimoto(1999a) found the antimony-ore deposit remains at the north slope of Mt. Amatsutsumi, Nishimera-mura, Koyu-gun, Miyazaki Prefecture. After that Fujimoto(1999b), Senba(2000), Yamanaka & Fujimoto (2001) and Hiramatsu et al. (2001) reported some minerals from that ore deposit remains. In 2002 we surveyed the area, took some ore samples and investigated them by microscopy, X-ray diffraction and electron probe micro analysis. Main ore minerals are stibnite, stibiconite, pyrite and sphalerite. In druse there exists a red colored transparent little mineral with diamond luster on stibnite crystal. It is decided pyrargyrite (Ag3SbS3) by X-ray diffraction, ore microscopy and electron probe micro analysis. As other druse mineral, a light yellow colored one with radial elongation associated with stibnite is found and is identified to be valentinite by the X-ray diffraction. By ore microscopy we found two silver minerals coexisted with stibnite. They are polybasite and miargyrite, which have the composition of (Cu,Ag,Fe)12Sb4S13 and (Ag,Cu,Fe)SbS2, respectively. Judging from the presence of only pyrite as for the Fe-S system mineral and the low iron content (1.5 atomic %) in sphalerite, it is considered that this antimony ore deposit was formed by the high sulfur fugacity ore solution.
