metamorphic

Tumbled limestone or calcitic marble

Calcite-rich carbonate rock; primarily calcium carbonate (CaCO₃)

AI-generated identification · may be incorrect

Cream to honey colored, opaque, with a smooth tumbled surface and porous/vuggy texture. Calcite has Mohs hardness 3, vitreous to dull luster, rhombohedral cleavage, and relatively low specific gravity (~2.7); it effervesces in dilute hydrochloric acid.

Identified September 16, 2026More metamorphic →

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Physical properties

Formation & geological history

Likely formed from marine carbonate sediment, later lithified or mildly metamorphosed; its exact geological age cannot be determined from the photograph. The rounded shape and polish indicate human tumbling.

Uses & applications

Used as a decorative or educational specimen, landscaping stone, and occasionally in carvings; calcitic marble is also used for tile, aggregate, and building stone. This small common piece generally has little commercial value.

Geological facts

The cavities may represent dissolved fossils, shell fragments, or weathered carbonate grains. Calcite can be distinguished from quartz by its much lower hardness and acid reaction.

Field identification & locations

Common in limestone and marble regions worldwide, including the United States, Mexico, Europe, and Southeast Asia. Test only an inconspicuous spot: a steel nail may scratch it, and weak acid should fizz.