Sphalerite, chalcopyrite, tetrahedrite and galena. Ainai Mine, Akita Prefecture, Japan

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Large sphalerite (grey) crystals are separated by intergrown chalcopyrite (yellow, centre), galena (white, centre) and tetrahedrite (green-blue, centre). Tetrahedrite and galena form rims about chalcopyrite. Chalcopyrite inclusions within sphalerite are both irregular in shape (bottom centre) and submicroscopic where they change the surface colour of the sphalerite (light blue-grey diffuse areas, top centre). Faint reddish-grey areas in sphalerite (centre top) are also due to submicroscopic inclusions, probably of tetrahedrite, which are known to give sphalerite red internal reflections. Black areas are gangue phases.

Polished block, plane polarized light, x 160, oil

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