Millerite

specimen number:
2063335

location:
Bayport Quarry, Huron Co., Michigan, USA

description:
An open pocket across the front of this matrix is lined with crystalline calcite and partially filled with metallic acicular crystals of millerite. Collected by Keith Hayes in 1986. The specimen comes with a previous label from the collection of Ray DeMark.

Located in Huron County, Michigan, the Bayport Quarry exposes the Mississippian-aged Bayport Limestone Formation, a sedimentary unit composed primarily of fossiliferous limestone, dolomite, and chert nodules. Commercial quarrying operations began in the late nineteenth century around the 1880s, serving as a major regional source of industrial crushed stone, aggregate, and agricultural lime. Over its long operating history, the locality gained immense popularity among rockhounds and mineral collectors for producing fine specimens of millerite, pyrite, marcasite, calcite, dolomite, quartz crystals, and fossilized marine organisms embedded within the rock, as well as distinctive concentric chert nodules historically valued by Native Americans for toolmaking.

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