Quartz after Calcite with Chalcopyrite

specimen number:
2312595

location:
Boldut Mine, Cavnic, Maramures Co., Romania

description:

Sparkling colorless crystals of quartz forming replacements after now gone groupings of calcite crystals before .0 cm in size, these on a crystallized chalcopyrite matrix. This is in terrific condition.

The Boldut Mine, located within the Cavnic mining district of Maramures County, Romania, is part of a historic mining region with roots dating back to medieval times and earlier, while intensive industrial extraction of its polymetallic ores operated heavily through the 20th century until final closure around 2005. Geologically, the deposit sits within the Neogene volcanic belt of the Inner Carpathians, where hydrothermal activity driven by calc-alkaline magmatism emplaced rich veins of lead, zinc, copper, gold, and silver into volcanic and sedimentary host rocks. The underground workings became internationally renowned among mineral collectors for producing diverse sulfide and carbonate assemblages, including quartz, dolomite, rhodochrosite, calcite, sphalerite, and galena.

Quartz after calcite pseudomorphs are fascinating mineral specimens where quartz has completely replaced an earlier crystal of calcite while preserving its original geometric form. Geologically, these formations typically occur when hydrothermal fluids or silica-rich groundwater circulate through a rock cavity containing preexisting calcite crystals, altering the chemical environment. Mineralogically, the acidic or changing conditions cause the calcite to dissolve entirely, creating a hollow mold or leaving a void that is subsequently filled or coated by microcrystalline quartz or chalcedony. This process results in a durable quartz replica that retains the distinct rhombohedral or scalenohedral shapes characteristic of the original calcite crystals.

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