gemstone
Blue Sapphire
Corundum (Al2O3)
Hardness: 9 on Mohs scale, Color: Blue, Luster: Adamantine to vitreous, Crystal Structure: Trigonal, Specific Gravity: 3.98 - 4.10
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Physical properties
Hardness: 9 on Mohs scale, Color: Blue, Luster: Adamantine to vitreous, Crystal Structure: Trigonal, Specific Gravity: 3.98 - 4.10
Formation & geological history
Formed in metamorphic or igneous rocks, specifically in aluminum-rich and silica-poor environments like pegmatites or marble, over millions of years.
Uses & applications
Used primarily in fine jewelry, watch components, scientific instruments, and high-durability windows.
Geological facts
Sapphire is the precious variety of corundum. While most famous for its deep blue color caused by iron and titanium impurities, sapphires actually occur in all colors except red (which is called ruby).
Field identification & locations
Identified by its exceptional hardness (second only to diamond), high density, and trigonal crystal habit. Commonly found in Sri Lanka, Madagascar, Myanmar, and Australia.
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