Chalcocite, bornite. chalcopyrite and covelline. El Salvador, Chile
Bornite (red-brown, centre) contains abundant chalcopyrite (yellow) as spindles parallel to (100) and as rounded inclusions (centre right). Bornite has extensively altered to blue chalcocite (light blue), but chalcopyrite has been preserved. Chalcocite itself has altered to covelline (dark blue, centre bottom) along its margin. Quartz (dark grey, bottom centre) is the main gangue. A single crystal of malachite (medium grey, centre right) has grown into a void.The bornite-chalcopyrite intergrowth is a replacement or exsolution texture but can be seen to be earlier than the replacement of bornite by chalcocite.
Polished block, plane polarized light, x 160, oil