Auction Win: Calcite with Marcasite

Locality: Linwood Mine, Buffalo, Scott County, Iowa, USA

Size: Cabinet - 10.2 × 8.2 × 3.9 cm

Calcite is the principal carbonate mineral with the chemical formula CaCO3, composed of calcium and carbonate. It is a major component of limestone, which is used in construction aggregates and to produce cement for everyday buildings.

Marcasite is a brassy iron sulfide mineral (FeS2) often found replacing calcite crystals, with its name derived from the French word for “mineral” and first described in the 18th century.

The Linwood Mine, located in Buffalo, Scott County, Iowa, is an open pit and underground limestone mine that began operations in 1918 and is geologically known for producing exceptional Calcite, Barite, and Marcasite specimens. This locality has yielded superb Calcite crystals up to 12.1 cm and diverse Barite forms including small tabular crystals, 5 cm coffin-shaped doubly terminated crystals, tan bladed crystals, and dendritic specimens. Collectors today value the Linwood Mine for its high-quality contemporary Barite and Calcite, which remain sought despite the mine's modest annual production of 1.4 million tons and long-term reserves. The site continues to impress with its fine mineral specimens, making it a relevant and notable destination for serious collectors of Iowa minerals.