Kuroko ores

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

Coarse-grained sphalerite (light grey) is the main sulphide and is rimmed by chalcopyrite (yellow, centre right) and galena (white, bottom centre, top right). The galena carries small inclusions of tetrahedrite (grey, lower reflectance, centre right), which are difficult to see, and euhedral pyrite (centre right). Small euhedral pyrite cubes (light yellow, bottom right) are associated with small galena and chalcopyrite crystals within sphalerite (top and bottom right). Gangue phases are grey.

Polished block, plane polarized light, x80, air

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

Coarse-grained sphalerite (light grey, centre) crystals carry tetrahedrite (green-grey, bottom centre), chalcopyrite (yellow, centre) and galena (white, centre) inclusions. Many of the inclusions can be seen to be associated with crystal boundaries of the sphalerite; this is especially true of fine-grained tetrahedrite (left centre). Chalcopyrite, galena and pyrite form incomplete rims around sphalerite (top left), where most of the pyrite has been replaced by galena (right centre). Much of the tabular gangue (grey, top centre) is baryte. Galena looks blue and darker against pyrite (right centre) but white and lighter against tetrahedrite within sphalerite (centre).

Polished block, plane polarized light, x 80, air

Galena, chalcopyrite, sphalerite and pyrite. Ainai Mine, Akita Prefecture, Japan

Repolished after etching. Galena (blue-white) forms complex intergrowths with chalcopyrite (yellow, centre) and sphalerite (light grey, right). Small subhedral pyrite crystals (light yellow-white, centre top) show high reflectance. Etching has shown the galena to comprise small polygonal crystals with 120' angles (centre top, centre bottom). Very small tetrahedrite crystals occur within galena (light grey, higher reflectance than sphalerite, left centre).

Polished block, plane polarized light, x 280, air

Pyrite, chalcopyrite, galena, sphalerite and tetrahedrite. Ainai Mine, Akita Prefecture, Japan

Euhedral pyrite (light yellow-white, left) is intergrown with chalcopyrite (yellow, centre), galena (light blue-white, centre right) and tetrahedrite (green-blue, lower reflectance, harder than galena, centre right) and minor sphalerite (grey, centre top). A coarse-grained subhedral crystal of sphalerite (right bottom) encloses chalcopyrite and is itself enclosed within euhedral galena. Gangue phases are black.

Polished block, plane polarized light, x 160, oil

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

An unidentified native metal (cream-white, high reflectance, centre) occurs within galena (light blue-white, centre bottom) which has complex intergrowths with chalcopyrite (yellow, centre) and sphalerite (grey, centre right). A single crystal of tetrahedrite (green-blue, centre top left) is present. The sphalerite is inclusion-free. Gangue phases are black and include lath-shaped baryte (bottom right).

Polished thin section, plane polarized light, x 160, oil

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

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