gemstone

Tumbled purple-blue corundum, possibly sapphire

Corundum (Al₂O₃); blue-to-purple varieties are sapphire

AI-generated identification · may be incorrect

Small rounded, polished grain with bluish-purple color and subdued vitreous luster. Corundum has Mohs hardness 9, trigonal crystal structure, no true cleavage, and specific gravity about 4.0; the image alone cannot confirm identity.

Identified August 30, 2026More gemstone →

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Physical properties

Formation & geological history

Forms mainly in aluminum-rich, silica-poor metamorphic rocks and some igneous deposits; crystals may be concentrated in alluvial gravels after weathering. Ages vary widely, commonly Precambrian to Cenozoic depending on deposit.

Uses & applications

Used as an abrasive and, when transparent and attractive, as sapphire jewelry or a collector gem. This opaque tumbled piece is likely decorative rather than gem-grade.

Geological facts

Purple color may reflect iron, titanium, chromium, or vanadium; mixed blue-purple material is sometimes marketed as “color-change sapphire” only when verified by testing.

Field identification & locations

Field identification requires hardness testing, density, and ideally refractive-index or spectroscopy; it should scratch quartz but not be scratched by steel. Common sources include Sri Lanka, Madagascar, Myanmar, India, and Montana, USA.