sedimentary

Iron-stained limestone or coral fragment

Calcite-rich carbonate rock; chiefly CaCO₃ (exact identification is uncertain from the image)

AI-generated identification · may be incorrect

Small irregular, pale cream-to-pink fragment with rusty red-brown staining and a granular/possibly porous texture. Calcite has Mohs hardness 3, vitreous to dull luster, rhombohedral cleavage, and specific gravity about 2.7; it fizzes in dilute hydrochloric acid.

Identified August 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed as marine limestone or coral-derived carbonate sediment, later cemented and stained by iron oxides during weathering. Its geological age cannot be determined visually and may range from recent coral material to ancient limestone.

Uses & applications

Limestone is used for cement, aggregate, lime, soil amendment, and building stone; attractive pieces may be collected, but this fragment has little commercial value.

Geological facts

The pink-red coloration commonly comes from hematite or other iron-oxide coatings. A porous or cellular texture would favor coral or bioclastic limestone over dense crystalline marble.

Field identification & locations

Test a fresh surface with dilute acid: vigorous fizz indicates calcite. Inspect for fossils or coral-like chambers; a knife should scratch it more readily than glass. Common worldwide, especially in former marine environments.