mineral
Yellow Sapphire (Corundum)
Corundum (Aluminum Oxide, Al2O3)
Hardness: 9 on Mohs scale; Color: honey-yellow with slight iron staining; Luster: adamantine to vitreous; Crystal structure: hexagonal/trigonal; Specific gravity: 3.98-4.06.
- Hardness
- 9 on Mohs scale
- Color
- honey-yellow with slight iron staining
- Luster
- adamantine to vitreous
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Physical properties
Hardness: 9 on Mohs scale; Color: honey-yellow with slight iron staining; Luster: adamantine to vitreous; Crystal structure: hexagonal/trigonal; Specific gravity: 3.98-4.06.
Formation & geological history
Formed in metamorphic rocks like marble or gneiss, and igneous rocks like syenite. This specimen likely came from a secondary alluvial deposit where it was weathered and rounded.
Uses & applications
Highly valued as a gemstone in jewelry (birthstone for September) and used in industrial applications as an abrasive or for its optical properties.
Geological facts
Yellow sapphire is colored by trace amounts of iron. It is the second hardest natural substance on earth after diamond, making it extremely durable for daily wear in rings.
Field identification & locations
Look for the characteristic hexagonal crystal habit and extreme hardness (it will scratch glass and quartz easily). Commonly found in Sri Lanka, Madagascar, and East Africa.
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