Pyrite after Pyrrhotite

specimen number:
2072036

location:
Huanzala Mine, Huallanca, Ancash, Peru

description:
A cluster of what were once platy pseudo-hexagonal crystals of pyrrhotite, these now completely replaced by brilliant golden octahedral crystals of pyrite. this is quite attractive.

The Huanzala Mine, located in the Huallanca district of Ancash, Peru, is a major polymetallic deposit in the central Andes that has produced lead, zinc, and silver from hydrothermal vein and replacement mineralization hosted in limestone. Modern mining began in 1968 with the development of underground operations that follow high grade ore bodies formed by mineralizing fluids moving through structurally controlled zones. The geology reflects the interaction of intrusive activity with carbonate rocks, resulting in complex sulfide mineralization and well developed vein systems. The mine has remained an important producer for decades and is also known for its mineral specimens formed in open cavities within the ore.

Pseudomorphs are minerals that have replaced an earlier mineral while preserving the original external crystal form. In the case of pyrite after pyrrhotite, the original pyrrhotite is altered through chemical processes, often involving the introduction of sulfur and changes in oxidation conditions, causing pyrite to form in its place. This replacement can occur without destroying the original crystal shape, so the specimen retains the form of pyrrhotite while being composed of pyrite. Such pseudomorphs provide evidence of changing geochemical conditions within a deposit and illustrate how one mineral can transform into another over time.

Questions about this specimen?
Send an email or call us: 314-341-1811.