gemstone
Ruby and Sapphire Cluster Ring
Corundum (Al2O3)
Hardness: 9 on the Mohs scale. Color: Pinkish-red (ruby) and light purple/lavender (sapphire). Luster: Vitreous to adamantine. Crystal structure: Trigonal. Cleavage: None, parting on basal plane.
- Hardness
- 9 on the Mohs scale
- Color
- Pinkish-red (ruby) and light purple/lavender (sapphire)
- Luster
- Vitreous to adamantine
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Physical properties
Hardness: 9 on the Mohs scale. Color: Pinkish-red (ruby) and light purple/lavender (sapphire). Luster: Vitreous to adamantine. Crystal structure: Trigonal. Cleavage: None, parting on basal plane.
Formation & geological history
Formed in metamorphic and igneous rocks, typically in aluminum-rich and silica-poor environments like marbles, gneisses, and alkali basalts over millions of years.
Uses & applications
Used primarily in fine jewelry and high-end timepieces due to exceptional hardness and beauty.
Geological facts
Corundum is the second hardest natural mineral on Earth, surpassed only by diamond. Gemstone varieties of corundum other than red are all classified as sapphires.
Field identification & locations
Identified by high hardness, distinct crystal habits, and specific gravity. Corundum gemstones are sourced globally from regions such as Myanmar, Sri Lanka, Thailand, and East Africa.
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