mineral

Ruby

Corundum (Al2O3 with Chromium trace impurities)

Hardness: 9.0; Color: Red (ranging from pinkish to blood-red); Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (may show basal parting); Specific Gravity: 3.97–4.05

Hardness: 9
Color: Red (ranging from pinkish to blood-red)
Luster: Vitreous to sub-adamantine

Identified March 3, 2026More mineral →

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Physical properties

Formation & geological history

Formed in metamorphic environments like marble or basalts/gneiss under high heat and pressure, typically 500-800 million years ago for many major deposits. Formed when aluminum oxide crystallizes with trace amounts of chromium.

Uses & applications

Primarily used in high-end jewelry (one of the four precious stones), watch bearings (synthetic), laser technology, and high-precision scientific bearings.

Geological facts

The red color comes from chromium; the most sought-after shade is known as 'Pigeon's Blood' red. The Sunrise Ruby is the most expensive colored gemstone ever sold ($30.3 million). It is the birthstone for July.

Field identification & locations

Identify in the field by its extreme hardness (scratches everything but diamond) and six-sided crystal habit. Look for them in alluvial deposits or marble host rock. Found commonly in Myanmar, Sri Lanka, Thailand, and Mozambique.

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