gemstone
Ruby (faceted gemstone)
Corundum (Al2O3 with Cr impurities)
Hardness: 9 on Mohs scale. Color: Pigeon blood red to pinkish red. Luster: Vitreous to sub-adamantine. Crystal structure: Hexagonal/Trigonal. Specific gravity: 3.97–4.05.
- Hardness
- 9 on Mohs scale
- Color
- Pigeon blood red to pinkish red
- Luster
- Vitreous to sub-adamantine
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Physical properties
Hardness: 9 on Mohs scale. Color: Pigeon blood red to pinkish red. Luster: Vitreous to sub-adamantine. Crystal structure: Hexagonal/Trigonal. Specific gravity: 3.97–4.05.
Formation & geological history
Formed in metamorphic rocks (micaschist, gneiss) or marble through contact/regional metamorphism. Also found in secondary alluvial deposits.
Uses & applications
Primarily used as a precious gemstone in fine jewelry (rings, pendants). Synthetic rubies are used in lasers and high-precision mechanical parts (watch bearings).
Geological facts
Ruby is one of the four traditional precious stones. Its red color is caused specifically by the presence of the element chromium. Large, high-clarity natural rubies can be more valuable than diamonds of similar size.
Field identification & locations
Identify by its extreme hardness (scratches almost everything except diamond) and deep red glow under UV light (fluorescence). Commonly found in Myanmar, Thailand, Mozambique, and Sri Lanka.
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