Calcite

Lore & Background

Calcite is derived from the German Calcit, a 19th-century term from the Latin calx (lime) with the suffix -ite. It is a doublet of the word chalk. In archaeology and stone trade, the term alabaster is used not only for a variety of gypsum but also for a translucent variety of fine-grained banded calcite deposit. Calcite exhibits thermoluminescent properties mainly due to divalent manganese impurities, and its dissolution in acids produces characteristic effervescence.

Reader's Guide

Calcite is significant as the most stable polymorph of calcium carbonate and a major component of limestone, making it a key mineral in geology and industry. Its defining Mohs hardness of 3 and diagnostic properties such as vitreous luster, specific gravity of 2.71, and perfect rhombohedral cleavage aid in identification. Calcite's retrograde solubility—less soluble in water as temperature increases—and its reaction with carbon dioxide influence groundwater processes, leading to cave formation and karst topography. Its thermoluminescence, activated by manganese and lead ions, helps in geological correlation and age determination. Calcite is found worldwide, with notable deposits such as the Calcite Quarry in Michigan, the largest carbonate mine.

Did You Know?

• Calcite defines hardness 3 on the Mohs scale of mineral hardness.
• A transparent variety of calcite called Iceland spar is used for optical purposes due to its strong birefringence.
• Calcite exhibits retrograde solubility, becoming less soluble in water as temperature increases.
• The term calcite is derived from the German Calcit, from Latin calx (lime), and is a doublet of the word chalk.