Calcite after Gypsum

specimen number:
2312583

location:
Cavnic, Maramures Co., Romania

description:
A neat pseudomorph specimen, this an aesthetic cluster of what was once gypsum, this now replaced by white calcite. Secondary crystallized groupings of calcite are scattered throughout. This is in terrific condition all around with no points of attachment.

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.

Calcite pseudomorphs after gypsum represent a fascinating mineralogical phenomenon where calcium carbonate replaces an original crystal of calcium sulfate while perfectly preserving its external form. Geologically, these specimens typically form in sedimentary evaporite deposits or lacustrine environments when changing chemical conditions, groundwater movement, or shifts in pH cause the pre-existing gypsum crystals to dissolve or react with carbonate-rich fluids.

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