mineral

Corundum (Sapphire and Ruby)

Aluminum Oxide (Al2O3)

AI-generated identification · may be incorrect

Hardness: 9 on the Mohs scale. Color: Blue (Sapphire) and Red (Ruby). Luster: Adamantine to Vitreous. Crystal Structure: Hexagonal/Trigonal. Specific Gravity: 3.95-4.10.

Hardness: 9 on the Mohs scale
Color: Blue (Sapphire) and Red (Ruby)
Luster: Adamantine to Vitreous

Identified June 17, 2026More mineral →

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Physical properties

Hardness: 9 on the Mohs scale. Color: Blue (Sapphire) and Red (Ruby). Luster: Adamantine to Vitreous. Crystal Structure: Hexagonal/Trigonal. Specific Gravity: 3.95-4.10.

Formation & geological history

Formed in aluminum-rich metamorphic rocks (schist, gneiss) or igneous rocks (nepheline syenite, pegmatite). Often found in alluvial deposits (river sands).

Uses & applications

Primarily used as high-end gemstones in jewelry. Industrial-grade corundum is used as an abrasive (emery) and in scratch-resistant windows or lasers.

Geological facts

Sapphire and Ruby are both variations of the mineral Corundum; the red color in rubies comes from Chromium, while sapphires get blue from Iron and Titanium.

Field identification & locations

Identified by extreme hardness (scratches almost everything except diamond). Commonly found in Myanmar, Sri Lanka, Madagascar, and Thailand. Look for hexagonal barrel-shaped crystals.