Ore deposit type: Magmatic-hydrothermal, porphyry type
Provenance: Assarel Mine, Bulgaria
Description: Altered porphyric igneous rock, cut by a stockwork of quartz veins (white) rich in chalcocite (black anhedral crystals). Stockwork zones in porphyry-type deposits are produced by hydrofracturing due to overpressurisation of magmatic-hydrothermal fluids. They generally occur above the intrusion and in its country rocks.