mineral

Tumbled tan stone, likely calcite or limestone

Calcite (CaCO₃), possibly microcrystalline limestone

AI-generated identification · may be incorrect

Pale tan, opaque, dull to weakly waxy luster, and rounded from tumbling; calcite has Mohs hardness 3, rhombohedral cleavage, and specific gravity about 2.71. The image alone cannot confirm composition or distinguish it from similar soft carbonate rocks.

Identified August 28, 2026More mineral →

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Physical properties

Formation & geological history

Carbonate minerals form by precipitation from groundwater or seawater, biological accumulation, or alteration of limestone; ages may range from modern to hundreds of millions of years. The specimen has been human-shaped or tumbled.

Uses & applications

Common calcite and limestone are used for cement, aggregate, soil conditioning, and building stone; attractive pieces may be sold as inexpensive decorative specimens.

Geological facts

Calcite effervesces visibly with dilute hydrochloric acid, while dolomite reacts weakly unless powdered. A steel nail can scratch it, helping distinguish it from harder quartz.

Field identification & locations

Likely sources include sedimentary carbonate regions worldwide, especially Mexico, the United States, Europe, and North Africa. Test an inconspicuous spot with vinegar or acid, observe cleavage, and compare hardness; identification remains provisional without testing.