Chalcopyrite, sphalerite, pyrite and mackinawite. Nigadoo River, New Brunswick, Canada
Sphalerite (grey, bottom left) contains submicroscopic chalcopyrite inclusions (yellow-grey areas) and is intergrown with chalcopyrite (yellow, right) which carries sphalerite exsolution stars (top right). Pyrite (light yellow-white, top right) is euhedral or has been replaced by chalcopyrite (centre). Mackinawite (brown, centre) is intergrown with chalcopyrite and shows polysynthetic twins (oriented north-south), some of which have a colour and reflectance that is very similar to the host chalcopyrite. Black areas are polishing pits.
Polished block, plane polarized light, x 180, air