Sphalerite with Calcite, Galena

specimen number:
2262074

location:
Naica, Chihuahua, Mexico

description:
Lustrous black crystals of sphalerite to almost 1.0 cm in size with crystallized galena across the top of a rhombohedral calcite crystal matrix. In good condition with very minimal damage present. The calcite crystals are brightly fluorescent red under longwave ultraviolet light.

The Naica Mine, located in the Saucillo Municipality of Chihuahua, Mexico, is a world-renowned skarn-hosted polymetallic deposit situated within a thick sequence of Cretaceous limestones. Geologically, the ore bodies consist of high-temperature replacement chimneys and mantos rich in lead, zinc, and silver, which were formed by hydrothermal fluids associated with Tertiary-aged felsic intrusions. The mine is most famous for its giant selenite gypsum crystals found in peripheral caverns, such as the Cave of Crystals, where stable hydrothermal conditions allowed crystals to grow to lengths exceeding 11 meters. Historically, mining and quarrying in the Naica district began with the discovery of silver by early prospectors in 1794, but large-scale industrial operations did not commence until the late 19th century. The mine was significantly developed by the Penoles company throughout the 20th century and remained a major producer of base metals until a massive flooding event in 2015 led to the suspension of most underground operations. As of 2026, Naica remains a site of immense geological and mineralogical importance, serving as a primary case study for the formation of massive sulfide deposits and spectacular secondary selenites.

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