mineral

Calcite

Calcite (calcium carbonate, CaCO₃), likely massive or crystalline limestone-derived material

AI-generated identification · may be incorrect

Cream to honey-yellow, translucent to opaque, with a vitreous to pearly luster and irregular crystalline texture; Mohs hardness 3, perfect rhombohedral cleavage, and specific gravity about 2.71. It effervesces strongly in dilute hydrochloric acid.

Identified August 23, 2026More mineral →

Explore Calcite in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms in sedimentary limestones, hydrothermal veins, caves, and evaporite environments through precipitation or alteration. Calcite occurs from ancient Precambrian deposits to modern cave and spring deposits; the specimen’s exact age cannot be determined visually.

Uses & applications

Used to manufacture cement, lime, aggregate, and industrial fillers; clear crystals are collected and occasionally used ornamentally. This rough specimen has modest decorative and educational value.

Geological facts

Calcite is one of Earth’s most abundant minerals and commonly displays double refraction in transparent crystals. Its color may result from iron, organic matter, or other impurities.

Field identification & locations

Common worldwide, especially in limestone regions and hydrothermal districts. Confirm with a copper coin or fingernail-scale hardness comparison and an acid test; avoid acid if preservation matters.