Calcite

specimen number:
2013556

location:
Auglaize Quarry, Junction, Ohio, USA

description:
Lustrous light yellow gem crystals of scalenohedral calcite to 5.0 cm in height coming nicely off matrix. In good condition. From the late 1970s.

The Auglaize Quarry, located near Junction in Paulding County, Ohio, is a premier mineral locality famous for its distinctive iridescent fluorite. Geologically, the quarry exposes Middle Devonian carbonate rocks, specifically the Dundee Limestone and the overlying Silica Formation. The mineralization is associated with the findlay Arch, where hydrothermal fluids moving through the sedimentary sequence deposited minerals in vugs and fractures within the limestone. While primarily an industrial limestone quarry producing aggregate and agricultural lime, it gained international fame for producing dark brown to amber fluorite crystals that often exhibit a vibrant purple or blue iridescence caused by microscopic inclusions or surface coatings. Historically, the quarry has been in operation for many decades, with significant mineralogical interest peaking during the mid to late 20th century as collectors and museums sought out its unique specimens. Although access has become more restricted in recent years, the site remains a classic reference locality for Midwestern Mississippi Valley-Type (MVT) mineralization.

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