Quartz after Calcite with Pyrite

specimen number:
2312219

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

description:

Classic for this locality, large scalenohedral crystals of what were once calcite measuring to almost 10.0 cm incisor coming off matrix with pyrite. The calcite crystals are now gone and replaced completely by sparkling colorless crystals of quartz. In terrific condition all around.

The Boldut Mine, situated in the Cavnic mining district of Maramures County, Romania, is part of a historic polymetallic extraction center with roots dating back centuries. Geologically, the deposit lies within the Neogene volcanic belt of the Eastern Carpathians, where complex hydrothermal vein systems cut through volcanic and sedimentary host rocks. These epithermal solutions deposited rich concentrations of lead, zinc, copper, gold, and silver ores. Beyond its industrial mining history, the Boldut Mine is internationally famous among mineral collectors for producing magnificent specimens of quartz, rhodochrosite, and carbonates in association with various sulfide minerals such as pyrite, sphalerite, and galena.

Pseudomorphs occur when one mineral replaces another while preserving the original crystal shape. A classic example is quartz after calcite, where quartz gradually dissolves or replaces an existing crystal of calcite. As the replacement happens, the incoming silica takes on the exact geometric form of the original calcite crystal. This results in a specimen that has the internal composition of quartz but the external crystal habit of calcite.

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