Bornite, pyrite and chalcopyrite. Aarja, Oman
250µm
Radiating pyrite aggregates (light yellow-white, centre top) have been fractured and cemented by quartz (top centre). They have been extensively replaced by bornite (brown, centre), which locally is intergrown with minor amounts of chalcopyrite (yellow, centre left). In the cores of the original pyrite aggregates, where bornite replacement is complete, there is an almost total absence of relict pyrite. Bands of bornite (top left) between pyrite are probably fracture infilling rather than replacement. Quartz (grey) is the gangue.
Polished thin section, plane polarized light, x 80, air
