Calcite

Physical Properties

Hardness: 3 on Mohs scale; Color: Grayish-white (can be various depending on impurities); Luster: Vitreous to pearly; Crystal Structure: Trigonal (rhombohedral cleavage); Specific Gravity: 2.71

Formation & Geological History

Primary constituent of sedimentary rocks like limestone. Formed through chemical precipitation from sea water or groundwater, or biological processes (shells). Can form in various geological ages including Paleozoic to Cenozoic.

Uses & Applications

Used in the manufacture of cement and lime for the construction industry, as a soil conditioner in agriculture, and high-purity specimens are used in optical instruments.

Geological Facts

Calcite is one of the most common minerals on Earth. It exhibits a unique optical property called double refraction, where a single beam of light passing through it is split into two.

Field Identification & Locations

Identify in the field by its rhombohedral cleavage (it breaks into tilted cubes) and its rapid effervescence (bubbling) when a drop of weak hydrochloric acid or vinegar is applied. Commonly found in limestone quarries and caves.

Identified on: 5/2/2026

Mode: Standard