sedimentary

Likely calcite-rich limestone

Calcite (CaCO₃), probably micritic or fossiliferous limestone

AI-generated identification · may be incorrect

Pale cream-gray, rough and granular with dull to slightly vitreous luster; calcite hardness is 3 Mohs, with excellent rhombohedral cleavage. Low-to-moderate density (about 2.7 g/cm³); identification is tentative from the photograph.

Identified August 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Limestone forms when marine carbonate mud, shells, or reef material accumulate and lithify, commonly in shallow seas; its exact geological age cannot be determined visually. A small irregular piece may also be weathered calcite-rich material.

Uses & applications

Used for cement, aggregate, agricultural lime, building stone, and neutralizing acidic soils; attractive crystalline pieces may be collected, but this specimen appears non-gem quality.

Geological facts

Calcite strongly effervesces with dilute hydrochloric acid or household vinegar, especially when powdered or freshly scratched. Its cleavage and relatively low hardness distinguish it from quartz.

Field identification & locations

Common worldwide, especially in former marine basins; major sources include the United States, Mexico, Europe, and China. Test a fresh surface with vinegar, check whether it scratches with a copper coin, and inspect for fossils or visible cleavage.