mineral

Ruby (Corundum)

Aluminum oxide (Al2O3) with Chromium traces

Hardness: 9 on Mohs scale; Color: Pinkish-red to pigeon-blood red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal; Cleavage: None (has parting); SG: 3.97-4.05

Hardness: 9 on Mohs scale
Color: Pinkish-red to pigeon-blood red
Luster: Vitreous to sub-adamantine

Identified May 25, 2026More mineral →

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Physical properties

Hardness: 9 on Mohs scale; Color: Pinkish-red to pigeon-blood red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal; Cleavage: None (has parting); SG: 3.97-4.05

Formation & geological history

Formed in metamorphic rocks such as marble or schist, and in igneous rocks like basalt. Found in contact metamorphic zones where aluminum-rich magma meets limestone.

Uses & applications

Primarily used as a gemstone in high-end jewelry and as a July birthstone. Industrial uses include lasers, watches (bearings), and high-precision instruments due to its hardness.

Geological facts

Ruby is the red variety of the mineral corundum; every other color is called sapphire. The red color is caused specifically by chromium substituting for aluminum.

Field identification & locations

Identify by its extreme hardness (scratches glass/steel easily) and characteristic red fluorescence under UV light. Common sources include Myanmar, Madagascar, Thailand, and Mozambique.

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mineral