mineral
Sapphire
Corundum (Al2O3)
AI-generated identification · may be incorrectHardness: 9 on Mohs scale; Color: Deep blue; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None; Specific Gravity: 3.95-4.03.
- Hardness
- 9 on Mohs scale
- Color
- Deep blue
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 9 on Mohs scale; Color: Deep blue; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None; Specific Gravity: 3.95-4.03.
Formation & geological history
Formed in metamorphic rocks (schist, gneiss) or igneous rocks (basalt, syenite) under high pressure and temperature. Large crystals often concentrate in alluvial deposits.
Uses & applications
Primary use in fine jewelry; industrial applications include high-durability windows (watch crystals), semiconductor wafers, and high-performance lasers.
Geological facts
Sapphire is the second hardest natural substance on Earth after diamond. While blue is most famous, sapphires occur in every color except red (which are rubies).
Field identification & locations
Identify by its extreme hardness (will scratch glass/steel easily) and high density; common sources include Sri Lanka, Madagascar, Myanmar, and Montana, USA.
