Appalachian metamorphosed sulphides

Pyrrhotite, sphalerite, chalcopyrite and graphite. Great Gossan Lead, Virginia, USA

Pyrrhotite (brown) shows deformation twin lamellae (higher reflectance, centre top) and plucking along its (0001) cleavage (black pits, centre top). Both inclusion-free sphalerite (light grey, centre bottom) and sphalerite with abundant chalcopyrite (yellow) inclusions along crystallographic directions (top right) are present. A curved flake of graphite (brown, low reflectance, centre) lies across a pyrrhotite-sphalerite junction close to a silicate grain. Black areas are polishing pits.

Polished block, plane polarized light, x80, air

Pyrrhotite, pyrite, magnetite and chalcopyrite. Ducktown, Tennessee, USA

Subhedral to euhedral magnetite (light grey, centre left) encloses rounded pyrrhotite (brown) inclusions. Pyrite (yellow-white, bottom right) is enclosed within pyrrhotite (brown) which shows metamorphic cleavage (top right), some of this cleavage penetrates pyrite (top left, centre bottom). Thin rims of chalcopyrite (yellow, bottom centre) surround pyrite and magnetite. Black areas are polishing pits.

Polished block, plane polarized light, x40, air

Sphalerite, chalcopyrite, pyrrhotite and galena. Great Gossan Lead, Virginia, USA

Sphalerite (light grey, right) has chalcopyrite inclusions aligned along crystallographic directions and about grain boundaries. Hence, it shows chalcopyrite disease. It is rimmed by chalcopyrite (yellow, centre) and pyrrhotite (brown, top left), together with minor galena (white, centre bottom). Dark grey area is silicate, black areas are polishing pits.

Polished block, plane polarized light. x40, air

Pyrite, sphalerite and galena. Cofer deposit, Virginia, USA

Euhedral to subhedral pyrite (yellow-white) contains small inclusions of galena (bottom left). Galena (blue-white) also occurs at the triple junction between three pyrite crystals (centre). Subhedral to anhedral sphalerite (light grey, top right) is present within a silicate (dark grey) gangue. Black areas are polishing pits.

Polished block, plane polarized light, x 80, air

Pyrite, sphalerite and chalcopyrite. Cofer deposit, Virginia, USA

Pyrite (yellow-white, right) is fractured along its cleavage and rimmed by chalcopyrite (yellow) and inclusion-free sphalerite (light grey, bottom left). Pyrite encloses lath-shaped phyllosilicates (dark grey, centre). Silicates are dark grey. Black areas are polishing pits.

Polished block, plane polarized light, x 40, air

Pyrite, pyrrhotite, magnetite and chalcopyrite. Ducktown, Tennessee, USA

Pyrite (yellow-white, top) is surrounded by pyrrhotite (brown, top right), showing cleavage (black, top right), or forms small euhedral crystals within pyrrhotite (bottom left). Magnetite (light grey, top left) is euhedral and has pyrrhotite inclusions (bottom right). Amphibole (dark grey) has a partial rim of chalcopyrite (yellow, centre left) and inclusions of chalcopyrite, pyrrhotite and pyrite.

Polished block. plane polarized light, x 40, air