PYRITE
ABOUT THE SPECIMEN
A classic example of the symmetric pyrite cubes that the Victoria Mine is known for. The intergrown cubes are positioned excellently for an beautiful display. Like most pieces from this locale, the cubes have been glued onto the original marl matrix and stabilized, though all of it is natural and the pyrite is situated as it was when it came out of the mine. This is a specimen that adds instant character to any display case.
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The Victoria Mine sits within the eastern Cameros Basin, a Late Jurassic–Early Cretaceous extensional rift filled with continental sediments subsequently subjected to low-grade hydrothermal metamorphism; Alonso-Azcárate et al. (1999) documented fluid migration pathways and sulfur isotope geochemistry confirming that pyrite formation resulted from reducing hydrothermal fluids circulating through the basin at temperatures between 124–265°C, with sulfur derived from the sedimentary sequence rather than a magmatic source. The resulting crystals are embedded in steeply inclined Cretaceous marl across three producing horizons averaging 2.5 meters thick - a soft, friable matrix that enabled open cubic growth with minimal competition for space, and low levels of trace elements like copper or arsenic preventing crystal distortion. Slow growth rates under stable conditions produced the near-geometrically perfect mirror-bright cubes, ranging from 1 mm to rarely 20 cm, that prompted crystallographers to treat them as textbook expressions of cubic symmetry. The mine is operated solely for specimen production rather than ore extraction - a distinction unique among significant pyrite localities globally - with all matrix pieces requiring careful mechanical preparation and stabilization, as the soft marl releases crystals during collection. Most multi-cube clusters have been reassembled in their natural positions rather than composited, a repair practice McDougall Minerals documented in detail. Supply is ongoing but quality is deeply variable by pocket, and large crystals retaining mirror-bright faces without iron oxidation tarnish are consistently difficult to find.