sedimentary

Likely porous limestone (tufa or travertine)

Calcite-rich limestone, chiefly calcium carbonate (CaCO₃)

AI-generated identification · may be incorrect

Cream to tan, irregular and visibly porous, with a dull to slightly waxy surface; calcite hardness is 3 Mohs, rhombohedral crystal structure, and perfect cleavage. The photograph alone cannot confirm its composition.

Identified October 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when calcium carbonate precipitates from mineral-rich water, often around springs or in caves; its exact age and setting cannot be determined from the image.

Uses & applications

Limestone is used for building stone, cement, and lime; attractive pieces may be collected or used decoratively.

Geological facts

Calcite-rich limestone fizzes in dilute acid, a useful identification test; porous varieties often preserve casts of plants or other features.

Field identification & locations

Check for a scratchable surface and acid fizz; distinguish it from porous quartz-rich rock, which is harder and does not fizz. Limestone is widespread worldwide.