Arsenopyrite with Sphalerite, Pyrite

specimen number:
2062541

location:
San Antonio Mine, Santa Eulalia, Chihuahua, Mexico

description:
Metallic blocky lustrous silver crystals of arsenopyrite to 1.0 cm in size on a matrix of crystallized sphalerite and pyrite. In good condition. The specimen comes with a previous label from the collection of Ray DeMark.

The San Antonio Mine, located in the East Camp of the historic Santa Eulalia mining district in Chihuahua, Mexico, dates back to early Spanish colonial prospecting initiated around 1703, though the broader district was initially discovered in 1591. While parts of Santa Eulalia experienced intermittent lulls and periods of heavy revolutionary disruption, large-scale industrial operations at San Antonio developed significantly through the late 19th and 20th centuries, and the greater district continues to see active modern operations rather than a permanent closure. Geologically, the deposit sits within the ENE-trending San Antonio Graben where Cretaceous limestone and dolomite strata are cut by Oligocene felsite dikes. The East Camp is specifically characterized by symmetrically zoned, intrusion-cored skarns and peripheral massive sulfide replacement bodies that yield valuable metal ores.

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