mineral

Banded calcite/aragonite mineral specimen (tentative)

Calcite (CaCO₃), possibly with aragonite or crystalline carbonate growth

AI-generated identification · may be incorrect

Tan to cream, earthy-to-pearly luster with prominent cleavage and layered, elongated crystal faces. Calcite has Mohs hardness 3, rhombohedral cleavage, and specific gravity about 2.71; it fizzes strongly in dilute hydrochloric acid.

Identified August 9, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed by precipitation from carbonate-rich groundwater in a cavity, vein, or sedimentary environment; the specimen’s precise age cannot be determined from the photograph. The projecting pale crystal may represent later calcite growth.

Uses & applications

Calcite is used in cement, lime, construction aggregate, soil treatment, and optical applications; attractive crystals are collected but are generally not jewelry stones.

Geological facts

Calcite commonly forms scalenohedral (“dogtooth”) or rhombohedral crystals and may show curved or layered growth. Its cleavage surfaces can look flatter and more reflective than the rough brown matrix.

Field identification & locations

Look for three-way rhombohedral cleavage, low hardness, and acid effervescence; it can scratch with a steel knife but not glass. Common worldwide, especially in limestone caves, hydrothermal veins, and deposits in Mexico, the United States, Iceland, and China.