sedimentary

Weathered limestone fragment

Limestone, predominantly calcite (CaCO₃)

AI-generated identification · may be incorrect

Tan to brown, dull earthy luster, fine-grained and irregularly fractured; calcite hardness is Mohs 3, with weak-to-moderate cleavage and specific gravity about 2.7. The image is insufficient to confirm fossils or crystal texture.

Identified August 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed mainly from compacted and cemented marine carbonate mud or shell debris, commonly during Paleozoic–Cenozoic sedimentary periods. Weathering and dissolution produced the rough, porous appearance.

Uses & applications

Used extensively for aggregate, cement and lime production, building stone, and architectural surfaces; unexceptional fragments have little jewelry or collector use.

Geological facts

Calcite-rich limestone effervesces visibly when a drop of dilute hydrochloric acid or vinegar is applied, though vinegar may react slowly. Brown coloration commonly reflects iron-oxide staining or organic matter.

Field identification & locations

Common worldwide, especially in former shallow-marine regions; major occurrences include the Alps, Appalachians, Mediterranean basin, and China. Confirm with an acid test, softness, and possible powdery white streak; avoid testing valuable specimens.