Calcite (variety manganese-rich) on Quartz - Sheffler's Geode Mine, USA - large geode about 18 cm. The calcites are up to about 4.5 cm

Mineral: Calcite (variety manganese-rich) on Quartz
Locality: Sheffler's Geode Mine, St. Francisville, Clark County, Missouri, USA
Dimensions: large geode about 18 cm. The calcites are up to about 4.5 cm

Description: mined in the 1980s. Acquired by me about 8 years ago.