mineral

Ruby (Raw Corundum)

Corundum (Aluminum Oxide with Chromium), Al2O3:Cr

Hardness: 9 on Mohs scale. Color: Pink to blood-red. Luster: Vitreous to sub-adamantine. Crystal structure: Trigonal/Hexagonal. Cleavage: None (has parting). Specific gravity: 3.97-4.05.

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

Identified May 27, 2026More mineral →

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Physical properties

Hardness: 9 on Mohs scale. Color: Pink to blood-red. Luster: Vitreous to sub-adamantine. Crystal structure: Trigonal/Hexagonal. Cleavage: None (has parting). Specific gravity: 3.97-4.05.

Formation & geological history

Formed under intense heat and pressure in metamorphic rocks like marble or schist, or igneous rocks like basalt. Often found in secondary alluvial deposits after weathering.

Uses & applications

Primarily used in jewelry as a precious gemstone. Industrial uses include lasers, precision bearings in watches, and high-durability windows for scientific instruments.

Geological facts

The red color is caused by trace amounts of chromium. Ruby is the birthstone for July and is one of the four traditional 'precious' stones alongside diamond, sapphire, and emerald.

Field identification & locations

Identify by its extreme hardness (will scratch almost any other mineral except diamond) and hexagonal crystal habit. Common in Myanmar, Sri Lanka, Madagascar, and East Africa. Fluoresces red under UV light if chromium content is high.

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