Chalcopyrite, bornite, chalcocite, covelline and molybdenite. El Salvador, Chile




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250µm


Chalcopyrite (yellow, centre left) is intergrown with bornite (brown-orange, left centre) and lath-shaped molybdenite (light grey, top right). Both copper-iron sulphides have altered to chalcocite (light blue, left and bottom right), which itself has a covelline rim (dark blue) associated with malachite (grey, poorly polished, left). Thin chalcopyrite spindles along (100) of the host bornite (left) have been preserved in chalcocite replacing bornite (left centre). Chalcopyrite (top right) has altered about its margin and along a fracture to covelline which shows strong bireflectance and reflection pleochroism (light and dark blue, centre right).


Polished block, plane polarized light, x 80, air



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