gemstone

Tumbled ruby-bearing corundum (probable)

Corundum, aluminum oxide (Al₂O₃), colored red by chromium; possibly ruby

AI-generated identification · may be incorrect

Dark reddish-purple, opaque to translucent, with a polished/tumbled surface and vitreous luster. Hardness is Mohs 9, trigonal crystal structure, no true cleavage, and specific gravity about 4.0; the visible pits and inclusions suggest a low-grade specimen.

Identified August 22, 2026More gemstone →

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Physical properties

Formation & geological history

Corundum forms in aluminum-rich metamorphic rocks, especially marble and mica schist, or in igneous environments; ruby-bearing rocks commonly formed during Precambrian to younger metamorphic events. Red color results mainly from chromium impurities.

Uses & applications

Ruby-quality material is used in jewelry, while non-gem corundum is used as an abrasive and refractory. Small tumbled pieces are primarily sold as decorative or educational specimens.

Geological facts

The image is consistent with ruby/corundum but cannot confirm identity visually; dark garnet, jasper, or dyed stone are alternatives. A hardness or refractive-index test is needed for reliable identification.

Field identification & locations

Common sources include Myanmar, Sri Lanka, Mozambique, Afghanistan, Vietnam, India, and Madagascar. Corundum may scratch glass, but testing should be done carefully because a polished specimen can be damaged or misidentified.