Chalcopyrite with Quartz, Pyrite after Pyrrhotite

specimen number:
2312629

location:
Cavnic, Maramures Co., Romania

description:
Crystals of chalcopyrite to 0.8 cm in size across the top of a crystallized quartz matrix with pyrite replacing previous crystals of pyrrhotite. In good condition.

Cavnic, located in the Maramures region of northern Romania, is a historic mining district with metal extraction dating back to medieval times and sustained commercial operations through the twentieth century. Geologically, the area is situated within the Neogene volcanic belt of the Eastern Carpathians, where epithermal vein deposits formed through hydrothermal activity associated with calc-alkaline volcanism. Mineralogically, the district is world-famous for its rich polymetallic sulfide veins, producing exceptional, highly aesthetic museum specimens of quartz, rhodochrosite, calcite, sphalerite, galena, and various sulfosalts that are treasured by collectors globally.

Pyrite after pyrrhotite is a classic pseudomorph where iron disulfide replaces iron sulfide while preserving the original crystal morphology of the precursor mineral. Geologically, these transformations occur within hydrothermal veins, metamorphic rocks, or massive sulfide deposits when changing chemical conditions, such as rising sulfur activity or oxidation, destabilize pyrrhotite. Mineralogically, the resulting specimens typically retain the distinctive hexagonal or tabular crystal habits characteristic of pyrrhotite, while acquiring the brassy yellow metallic luster and cubic crystal system attributes of pyrite.

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