gemstone
Ruby (Faceted)
Corundum (Al2O3 with Cr trace elements)
Hardness: 9 on Mohs scale; Color: Red to pinkish-red; Luster: Adamantine to vitreous; Crystal structure: Trigonal; Cleavage: None (has parting); Specific gravity: 3.97-4.05
- Hardness
- 9 on Mohs scale
- Color
- Red to pinkish-red
- Luster
- Adamantine to vitreous
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Physical properties
Hardness: 9 on Mohs scale; Color: Red to pinkish-red; Luster: Adamantine to vitreous; Crystal structure: Trigonal; Cleavage: None (has parting); Specific gravity: 3.97-4.05
Formation & geological history
Formed in metamorphic rocks such as marble or schist, or in igneous rocks like basalt. Created through high heat and pressure during tectonic events. Quality stones often come from alluvial deposits.
Uses & applications
Primarily used in high-end jewelry (rings, pendants) and occasionally in mechanical applications like watch bearings or industrial lasers.
Geological facts
Ruby is the birthstone for July. The red color is caused specifically by chromium; if the corundum is any other color, it is classified as a sapphire.
Field identification & locations
In the field, look for a deep red color that doesn't change when viewed from different angles (pleochroism). Gem-quality rubies are often found in Myanmar (Burma), Madagascar, and Thailand.
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