mineral

Ruby

Corundum (Al2O3 with chromium impurities)

Hardness: 9 on the Mohs scale; Color: Red ranging from pinkish to blood-red; Luster: Vitreous to subadamantine; Crystal system: Trigonal/Hexagonal; Cleavage: None; Specific Gravity: 3.97-4.05

Hardness: 9 on the Mohs scale
Color: Red ranging from pinkish to blood-red
Luster: Vitreous to subadamantine

Identified May 23, 2026More mineral →

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Physical properties

Hardness: 9 on the Mohs scale; Color: Red ranging from pinkish to blood-red; Luster: Vitreous to subadamantine; Crystal system: Trigonal/Hexagonal; Cleavage: None; Specific Gravity: 3.97-4.05

Formation & geological history

Formed in metamorphic rocks (schist or marble) or as a result of contact metamorphism. Many originate from Tertiary deposits or older Precambrian metamorphic terrains.

Uses & applications

Primarily used in high-end jewelry, industrial lasers, watch bearings, and as scientific instrument components due to extreme hardness.

Geological facts

Rubies are the red variety of the mineral corundum; any other color of corundum is called sapphire. The presence of chromium is what creates the red color. Historically, ruby is known as the 'King of Precious Stones' in Sanskrit.

Field identification & locations

Identified by its high hardness (only diamond is harder) and characteristic red fluorescence under UV light. Found in Burma (Myanmar), Thailand, Sri Lanka, and Madagascar.