mineral

Ruby

Corundum (Al2O3 with Chromium traces)

Hardness: 9.0 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
Color: Red to pinkish-red
Luster: Adamantine to vitreous

Identified April 8, 2026More mineral →

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Physical properties

Hardness: 9.0 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, gneiss, and schist, or in igneous rocks like basalt. Created through high pressure and temperature in aluminum-rich environments with low silica.

Uses & applications

Primarily used as a gemstone in high-end jewelry. Industrial-grade rubies (mostly synthetic) are used in lasers, watch bearings, and precision instruments.

Geological facts

Ruby is the birthstone for July. The presence of chromium is what gives it its red color and causes it to fluoresce, making the color appear more vibrant under sunlight.

Field identification & locations

Identify by its extreme hardness (only diamond is harder) and characteristic silky 'silk' inclusions (rutile needles). Commonly found in Myanmar (Burma), Sri Lanka, Thailand, and Mozambique.