gemstone

Red coral (polished coral beads)

Corallium spp.; chiefly calcium carbonate (CaCO₃, calcite)

AI-generated identification · may be incorrect

Opaque, vivid red, polished and glossy, with no visible crystals; calcite hardness is about 3–4 Mohs. The small rounded pieces appear to be shaped beads, so cleavage and density cannot be assessed reliably from the image.

Identified October 3, 2026More gemstone →

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Physical properties

Formation & geological history

Coral is a biological marine material formed by colonial coral animals; precious red coral grows slowly in deep waters and accumulates skeletons over centuries to millennia. It is not an igneous, sedimentary, or metamorphic rock.

Uses & applications

Used for beads, jewelry, ornaments, and carving; it is relatively soft and can scratch or be damaged by acids.

Geological facts

Red coral’s color comes from natural pigments in its calcium-carbonate skeleton; coral harvesting is regulated in many regions.

Field identification & locations

A porous or branching internal structure and carbonate reaction can help distinguish coral from dyed stone, but polished beads require close inspection. Precious coral is found in the Mediterranean and parts of the Pacific and Indian oceans.