gemstone
Sapphire (Blue/Violet Rough)
Corundum (Al2O3)
Hardness: 9 on Mohs scale; Color: Blue to violet; Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Specific Gravity: 3.95-4.03.
- Hardness
- 9 on Mohs scale
- Color
- Blue to violet
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 9 on Mohs scale; Color: Blue to violet; Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Specific Gravity: 3.95-4.03.
Formation & geological history
Formed in metamorphic or igneous rocks (such as basalt or marble) high in aluminum and low in silica. This rough specimen likely originated from alluvial deposits.
Uses & applications
Used primarily in jewelry as a precious gemstone and in industrial applications for high-durability watch crystals and scientific instruments due to extreme hardness.
Geological facts
All colors of corundum except red are called sapphire; red corundum is ruby. Blue sapphires get their color from trace amounts of iron and titanium.
Field identification & locations
Identify by a high specific gravity (feels heavy for its size) and its ability to scratch glass or quartz easily. Common sources include Sri Lanka, Madagascar, and Montana, USA.
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