The Yokozuru, Suisho, Tokoya, Sotan, Zurine and Usagida deposits are distributed around Mt. San-notake. They are contact metasomatic hydrothermal ore deposits formed in the contact between the Paleozoic limestone and the Kawara granodiorite that intruded in the Cretaceous period. Skarn zones are divided into two main zones, clinopyroxene zone and garnet zone. Based on the mineral assemblages the former is subdivided into three zones, A-, B- and C-zones, and the latter into two zones, D- and E-zones. A-zone is composed of plagioclase, alkali feldspar, quartz, hornblende, clinopyroxene, actinolite and opaque minerals, B-zone of quartz, clinopyroxene, garnet and opaque minerals, and C-zone of clinopyroxene, garnet, calcite and opaque minerals. D-zone includes garnet, clinopyroxene, chlorite, epidote and opaque minerals, and E-zone garnet, calcite, epidote, actinolite, quartz and opaque minerals. Sulfide mineralization occurred in the C-, D- and E-zones, and limestone zone. The main ore minerals are chalcopyrite, pyrite, pyrrhotite and sphalerite. Many kinds of Bi-, Te- and Ag-minerals were also found in a small quantity. They are bismuthinite, native bismuth, tetradymite, hessite, wittichenite, gustavite, aleksite, cuprobismutite, cosalite, argentite and so on. The FeS content of sphalerite coexisting with pyrite and chalcopyrite ranges from 13.6 to 19.8 mol.%, and the composition of pyrrhotite coexisting with pyrite varies from 46.9 to 47.4 Fe at.%. Based on the main mineral assemblages and the chemical compositions of sphalerite and pyrrhotite, it is suggested that the temperature-sulfur fugacity condition of the mineralization in the San-notake district locates in the pyrite-stability field near pyrite-pyrrhotite univariant curve in high temperature (400°-500°C) and cuts the univariant curve between 350° and 300°C. At later stage many Bi-Te-Ag-Pb-Cu-Fe Ni-Co-S minerals were produced, and the temperature-sulfur fugacity condition is estimated to be around the bismuthinite-bismuth univariant curve.