Pyrite after Pyrrhotite with Siderite

specimen number:
2072339

location:
Herja Mine, Maramures Co., Romania

description:
Platy crystals of what were once pyrrhotite measuring to 3.0 cm in size, these now replaced by pyrite, scattered across the top of a siderite crystal matrix. In good condition with minimal damage present, nice for this Romanian classic.

The Herja Mine, located near Baia Mare in Maramures County, Romania, is a major hydrothermal lead-zinc deposit situated within the Neogene volcanic chain of the Oas-Gutai Mountains. Geologically, the mineralization is hosted in an intricate network of veins and lenses that penetrate sedimentary rocks and andesitic intrusions, formed by fluids associated with Miocene volcanic activity. The site is famous for its diverse mineralogy, particularly its distinctive pseudomorphs of pyrite after pyrrhotite; in these specimens, the original hexagonal plates of pyrrhotite were replaced by fine-grained or drusy pyrite, often resulting in complex, stepped, or "stacked" formations of brassy, metallic discs. Historically, mining and quarrying in the Herja district have a long legacy, with large-scale industrial extraction of base metals like lead, zinc, and silver intensifying during the 19th and 20th centuries. The mine operated as a significant state-run enterprise for many decades before industrial production officially ceased in 2006.

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