sedimentary

Black Limestone with Calcite Veining

Limestone (CaCO3) with Calcite (CaCO3) inclusions

Hardness: 3 on Mohs scale; Color: Charcoal black to dark gray matrix with white/cream veins; Luster: Dull to earthy (matrix) with vitreous veins; Structure: Fine-grained microcrystalline; Cleavage: Rhombohedral (in veins)

Hardness: 3 on Mohs scale
Color: Charcoal black to dark gray matrix with white/cream veins
Luster: Dull to earthy (matrix) with vitreous veins

Identified June 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed over millions of years by the accumulation of organic debris (shells, coral, algal) on the ocean floor. The white veins are secondary fractures filled by calcite precipitating from mineral-rich groundwater. Often Paleozoic or Mesozoic in age.

Uses & applications

Used primarily as decorative aggregate, architectural stone, floor tiles, and in jewelry as 'Black Marble' when polished. Historically used as a building material.

Geological facts

The dark color is often due to a high concentration of organic carbon or iron sulfides. When struck with a hammer, some dark limestones emit a distinctive fetid odor from trapped gasses.

Field identification & locations

Identified by its reaction (fizzing) with cold dilute hydrochloric acid. Commonly found in areas with ancient seabeds. For collectors, look for high-contrast 'lightning' patterns in the veining.

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