gemstone
Ruby / Red Corundum
Al2O3 (Aluminum Oxide with Chromium trace)
Hardness: 9.0 (Mohs scale); Color: Pinkish-red to deep blood red; Luster: Vitreous to sub-adamantine; Crystal system: Trigonal/Hexagonal; Cleavage: None (has parting)
- Hardness
- 9
- Color
- Pinkish-red to deep blood red
- Luster
- Vitreous to sub-adamantine
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Physical properties
Hardness: 9.0 (Mohs scale); Color: Pinkish-red to deep blood red; Luster: Vitreous to sub-adamantine; Crystal system: Trigonal/Hexagonal; Cleavage: None (has parting)
Formation & geological history
Formed in metamorphic rocks (schist, gneiss) or marble when aluminum-rich magma interacts with limestone, or found in alluvial deposits. They date from the Precambrian to Cenozoic eras.
Uses & applications
Primarily used in high-end jewelry, watch bearings (synthetic), and historical use in the first lasers.
Geological facts
The red color comes from chromium; without it, the mineral is simply a sapphire. Ruby is one of the four precious stones alongside diamond, sapphire, and emerald.
Field identification & locations
Identify by its extreme hardness (scratches glass/most minerals) and vibrant red hue. Found in Myanmar, Sri Lanka, Thailand, and East Africa. Best collected from gravel beds (alluvial).
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