sedimentary

Black Limestone with Calcite Veins

Carboniferous Limestone with Secondary Calcite Infill

Hardness: 3 (limestone/calcite); Color: Dark grey to charcoal black with white veining; Luster: Dull to sub-vitreous; Structure: Fine-grained matrix with crystalline fractures; Cleavage: Rhombohedral in veins.

Hardness: 3 (limestone/calcite)
Color: Dark grey to charcoal black with white veining
Luster: Dull to sub-vitreous

Identified July 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed over 300 million years ago in shallow marine environments from the accumulation of calcium carbonate. The white veins are secondary deposits formed when mineral-rich water filled cracks in the rock.

Uses & applications

Informally known as 'Wishing Stones' when veins form a complete circle; used in landscaping, decorative gravel, and construction aggregates.

Geological facts

The white veins are often much younger than the host rock, representing a history of tectonic stress that cracked the stone. Many specimens are found as river-worn or beach pebbles.

Field identification & locations

Can be identified by the dark, fine-grained matrix and bright white veins that react to weak hydrochloric acid (fizzing). Commonly found on beaches in the UK, Ireland, and Great Lakes regions.

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