gemstone
Ruby
Corundum (Al2O3)
Hardness: 9 on Mohs scale; Color: Deep red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Specific Gravity: 3.97-4.05.
- Hardness
- 9 on Mohs scale
- Color
- Deep red
- Luster
- Vitreous to sub-adamantine
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Physical properties
Hardness: 9 on Mohs scale; Color: Deep red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Specific Gravity: 3.97-4.05.
Formation & geological history
Formed under intense heat and pressure in metamorphic rocks like marble or igneous rocks like basalt. Most fine specimens come from marble-hosted deposits where low silica allows for aluminum oxide formation stained by chromium.
Uses & applications
Primarily used in high-end jewelry, precision timepieces (bearings), and industrial lasers (ruby lasers).
Geological facts
Ruby is the red variety of the mineral corundum; every other color of corundum is known as sapphire. The presence of chromium is what gives ruby its signature red hue.
Field identification & locations
Identify by its extreme hardness (only diamond can scratch it) and intense red color. Commonly found in Myanmar, Thailand, Sri Lanka, and Madagascar. Natural rubies often contain needle-like inclusions known as 'silk'.
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