Metamorphosed lead-zinc ores
Pyrrhotite and galena. Broken Hill, New South Wales, Australia
Pyrrhotite (brown, top) is coarse-grained and is intergrown with galena (white, centre left). Dark grey areas are gangue phases showing faint internal reflections (bottom).
Polished block. plane polarized light, x 80, air
Pyrrhotite, chalcopyrite, sphalerite and galena. Broken Hill, New South Wales, Australia
Coarse-grained pyrrhotite (brown, top left) is intergrown with chalcopyrite (yellow, top right) and sphalerite (light grey, bottom left). A small galena inclusion (white, centre) lies within silicate (dark grey).
Polished block, plane polarized light, x80, air
Sphalerite and galena. Broken Hill. New South Wales, Australia
Sphalerite (light grey, centre bottom) is intergrown with galena (white, centre) with triangular cleavage pits (black, right centre). Dark grey areas are gangue phases. Black areas are polishing pits.
Polished block, plane polarized light, x 80, air
Sphalerite (light grey, centre) is intergrown with galena (white, centre left). Chalcopyrite (yellow, centre top) forms an incomplete rim to sphalerite and is associated with bournonite (white rim to chalcopyrite, centre top) and tetrahedrite (white, centre top right). At this magnification, galena, tetrahedrite group minerals and bournonite cannot easily be distinguished in plane polarized light. Dark grey area is gangue.
Polished Block, plane polarized light, x 40, air
Sphalerite, chalcopyrite, bournonite and tetrahedrite group. Broken Hill, New South Wales, Australia
Sphalerite (light grey, bottom) has an incomplete rim of chalcopyrite (yellow, centre). Bournonite (blue-white, centre) rims chalcopyrite. Minor tetrahedrite (grey, centre left) is enclosed within bournonite (centre left) and has a lower reflectance. Dark grey area is gangue, black areas are polishing pits.
Polished Block, plane polarized light, x 160, oil
Sphalerite (grey, right) is partially rimmed by chalcopyrite (yellow, bottom left) and bournonite (blue-white, centre)Tetrahedrite (light brown-grey, centre) is enclosed within a rim of bournonite (blue-white), which has a slightly lower reflectance, but is better polished than the isolated crystal of galena (white, centre left). Dark grey area is gangue. Black areas are polishing pits.
Polished block. plane polarized light. x 160, oil