mineral

Yellow calcite fragment

Calcite (calcium carbonate, CaCO₃)

AI-generated identification · may be incorrect

Pale honey-yellow, translucent to opaque, with vitreous to pearly luster and prominent rhombohedral cleavage; Mohs hardness 3, nonmetallic, typically low specific gravity (~2.71). The triangular shape likely reflects cleavage or deliberate trimming.

Identified September 4, 2026More mineral →

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Physical properties

Formation & geological history

Forms in limestones, hydrothermal veins, caves, and sedimentary cavities through precipitation from carbonate-rich fluids. Calcite occurs from ancient Precambrian rocks to modern cave deposits; the image alone cannot establish age.

Uses & applications

Used in cement, lime, aggregate, glass manufacture, and as a carbonate filler; transparent colored crystals are collected and occasionally cut as decorative specimens, though this piece appears modest quality.

Geological facts

Calcite effervesces strongly with dilute hydrochloric acid or vinegar (best tested on an inconspicuous edge). It can be distinguished from quartz by its much lower hardness and cleavage.

Field identification & locations

Common worldwide, including Mexico, Iceland, the United States, and China; identify by rhombohedral cleavage, softness, and acid reaction. Avoid scratching polished surfaces during testing.