Sphalerite with Calcite

specimen number:
2312299

location:
Davis-Deardorff Mine, Hardin Co., Illinois, USA

description:
Good old timer from Illinois, lustrous twinned crystals of sphalerite measuring to almost 3.0 cm in size across the top of matrix with crystallized quartz. In very good condition.

The Davis-Deardorff Mine, situated in the Cave-in-Rock mining district of Hardin County, Illinois, was a prominent underground producer within the nation's premier fluorspar region. Geologically, the deposit formed as a stratabound replacement ore body within Mississippian-age limestone formations directly beneath sandstone layers. The mineralogy was dominated by high-grade fluorite, often accompanied by sphalerite, galena, barite, quartz, and various sulfide minerals. Active commercial development and shaft sinking in the area ramped up significantly around the mid-20th century, particularly from the 1950s through the 1970s, before regional underground mining ultimately ceased across the district in December 1995 due to rising operational costs and foreign competition.

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