sedimentary

Dark limestone or mudstone pebble with calcite veins

Fine-grained carbonate rock, likely limestone (dominantly calcite, CaCO₃); exact identification requires testing

AI-generated identification · may be incorrect

Dark gray, fine-grained, smooth water-worn surface with thin pale veins, likely calcite. Calcite has Mohs hardness 3 and rhombohedral cleavage; the host rock’s hardness and density vary.

Identified October 14, 2026More sedimentary →

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Physical properties

Dark gray, fine-grained, smooth water-worn surface with thin pale veins, likely calcite. Calcite has Mohs hardness 3 and rhombohedral cleavage; the host rock’s hardness and density vary.

Formation & geological history

Likely formed from compacted carbonate-rich sediment, then fractured and mineralized by calcite-bearing fluids; age cannot be determined from the image.

Uses & applications

Primarily a collecting or decorative pebble; limestone is widely used for cement, lime, and building stone.

Geological facts

The pale lines are consistent with mineral-filled fractures, commonly called veins.

Field identification & locations

Look for fizzing with dilute acid to test for calcite-rich limestone; a scratch test can help distinguish softer limestone from harder rocks. Similar pebbles occur in river, beach, and sedimentary-rock settings worldwide.