gemstone
Sapphire
Corundum (Al2O3)
AI-generated identification · may be incorrectHardness: 9 on the Mohs scale, Color: Various (commonly blue, but also yellow, green, pink, colorless), Luster: Vitreous to adamantine, Crystal structure: Trigonal, Cleavage: None (parting may occur), Specific gravity: 3.98-4.02
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Physical properties
Hardness: 9 on the Mohs scale, Color: Various (commonly blue, but also yellow, green, pink, colorless), Luster: Vitreous to adamantine, Crystal structure: Trigonal, Cleavage: None (parting may occur), Specific gravity: 3.98-4.02
Formation & geological history
Forms in igneous rocks like basalt and syenite, or in metamorphic rocks such as marble formed through regional or contact metamorphism. Often found in alluvial deposits due to its high resistance to weathering.
Uses & applications
Used primarily in fine jewelry, watch components, scratch-resistant glass, and industrial cutting and abrasive applications.
Geological facts
Sapphire is the gem variety of corundum. While blue is the most famous color, all non-red varieties of gem-quality corundum are classified as sapphires (with red being ruby).
Field identification & locations
Identified by its exceptional hardness (scratching quartz and topaz), high density, and trigonal crystal habit. Commonly sourced from Sri Lanka, Madagascar, Australia, and parts of the United States.
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