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Tochilinite and cuprian tochilinite from the Kamaishi mine,Iwate prefecture,Japan.

1980; Japan Association of Mineralogical Sciences; Volume: 75; Issue: 11 Linguagem: Inglês

10.2465/ganko1941.75.377

1883-0765

Yôichi Muramatsu, Matsuo Nambu,

Metal Extraction and Bioleaching

The first occurrence of tochilinite and its variety, cuprian tochilinite in Japan were found in the so called “high temperature skarn” consisting mainly of vesuvianite, tilleyite, titaniferous andradite and calcite in the Shinyama pyrometasomatic copper-iron ore deposit of the Kamaishi mine, Iwate Prefecture. Two minerals occur as microscopic irregular aggregates ranging from about 100 to 500 microns in size composed of fibrous fine crystals along cracks and grain boundaries of vesuvianite in intimate association with calcite, hexagonal pyrrhotite and sphalerite. Under the ore microscope, the reflection colour is yellowish brown. Reflection pleochroism is strong with colours changing from yellowish brown to yellowish grey, and also it is strongly anisotropic, with interference colours from pale yellowish brown to greyish white with yellowish tint. Reflectivities measured in air are: 486 nm 10.0-13.3%, 546 nm 10.2-14.9%, 589 nm 10.6-15.8%, 644 nm 10.8-17.6%. The polishing hardness is considerably lower than that of coexisting pyrrhotite, chalcopyrite and sphalerite. Optical properties of cuprian tochilinite resemble closely those of tochilinite above mentioned, actually indistinguishable from it. Electron microprobe analyses of two tochilinite grains and three cuprian tochilinite grains yield to the empirical formulae 2[Fe0.78-0.77S]⋅1.85-1.81[Mg0.79Al0.20Ca0.01(OH)2] and 2[Fe0.68-0.63Cu0.15-0.24S]⋅1.71-1.65[Mg0.78Al0.21-0.20Ca0.01-0.02(OH)2], respectively. The ore containing two minerals may be crystallized under the same condition as that of main copper ores at the Shinyama deposit. X-ray study could not be made due to its extremely small amounts of these minerals.