Calcite

specimen number:
2013568

location:
Linwood Mine, Buffalo, Scott Co., Iowa, USA

description:
A colorless translucent lustrous rhombohedral crystal of calcite set on a very thin small amount of matrix. This is in good condition.

The Linwood Mine, located near Buffalo in Scott County, Iowa, is one of the largest underground limestone operations in the United States. Its history began as an open-cut quarry at least as early as 1897, with formal operations under the Linwood name commencing around 1918. As the demand for high-purity limestone grew and the surface overburden became too thick to remove economically, the facility transitioned to underground room-and-pillar mining in 1956. Geologically, the mine exploits Middle Devonian strata, specifically the Otis and Pinicon Ridge Formations. The Otis Formation is prized for its exceptionally pure calcium carbonate, while the mine is also world-famous among collectors for its secondary mineralization. Large cavities and paleokarst features within the limestone have produced world-class specimens of calcite, marcasite, and barite. Unlike many historic mines, Linwood remains a highly active industrial site today, producing lime and aggregates for construction, agriculture, and water treatment.

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