mineral

Large calcite crystal cluster

Calcite (calcium carbonate, CaCO₃)

AI-generated identification · may be incorrect

Typically colorless to white, translucent, and vitreous to pearly, with prominent rhombohedral cleavage and Mohs hardness 3. The broad stepped faces and layered appearance are characteristic of calcite, though the specimen may include minor matrix minerals.

Identified August 10, 2026More mineral →

Explore Large calcite crystal cluster 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

Calcite commonly forms in hydrothermal veins, cavities, sedimentary limestones, and metamorphic marbles. Its age cannot be determined from the photograph; formation may range from recent mineral deposition to ancient Paleozoic or younger host-rock environments.

Uses & applications

Used industrially for cement, lime, aggregate, glass, and chemical production; clear crystals are collected and occasionally used ornamentally. This large cabinet specimen has primarily display value.

Geological facts

Calcite effervesces strongly with dilute hydrochloric acid and shows birefringence, producing doubled lettering when placed over text. It is one of the most abundant carbonate minerals.

Field identification & locations

Test for hardness with a copper coin or steel edge, cleavage, and acid reaction; avoid scratching attractive faces. Common sources include Mexico, Iceland, the United States, China, and Morocco.