gemstone

Raw ruby (likely corundum)

Corundum, Al₂O₃; red color caused mainly by chromium

AI-generated identification · may be incorrect

Mohs hardness 9; translucent to opaque pink-red, vitreous to greasy luster, trigonal crystal structure, and poor basal cleavage. The rough specimen shows irregular fracture and may contain inclusions or matrix.

Identified August 28, 2026More gemstone →

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Physical properties

Formation & geological history

Forms primarily in aluminum-rich metamorphic rocks such as marble and gneiss, or in some igneous environments; ruby deposits range from Precambrian to younger geological ages. This may also be pink corundum or heavily included ruby rather than gem-grade material.

Uses & applications

Gem-quality material is faceted or cabochon-cut for jewelry; lower-grade corundum is mainly collected as a mineral specimen. Synthetic ruby is used in lasers, watches, and scientific instruments.

Geological facts

Ruby and sapphire are the same mineral species; chromium produces the red color. Natural ruby commonly contains rutile, mica, calcite, or other inclusions, and uncut pieces can resemble red spinel or garnet.

Field identification & locations

Check for very high hardness, uneven red-to-pink color, and inclusions; a hardness test should not be performed on a valuable specimen. Common sources include Myanmar, Mozambique, Sri Lanka, Madagascar, Tanzania, and Vietnam.