gemstone

Ruby (Corundum)

Aluminum oxide (Al2O3) with Chromium traces

Hardness: 9.0 on Mohs scale; Color: Deep red to pinkish red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific gravity: 3.97-4.05

Hardness: 9
Color: Deep red to pinkish red
Luster: Vitreous to sub-adamantine

Identified July 16, 2026More gemstone →

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Physical properties

Hardness: 9.0 on Mohs scale; Color: Deep red to pinkish red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific gravity: 3.97-4.05

Formation & geological history

Formed in metamorphic rocks seperti marble or basaltic igneous rocks through high heat and pressure. The red color is caused by the presence of chromium substituting for aluminum in the crystal lattice.

Uses & applications

Primarily used in high-end jewelry, watchmaking (bearings), and as laser components due to its hardness and optical properties.

Geological facts

Ruby is one of the four traditional 'precious' stones. The most valuable rubies exhibit a 'pigeon blood' red color. In this image, the stone is cut 'en cabochon', which is common for stones with silk inclusions or stars.

Field identification & locations

Identify by its extreme hardness (scratches glass/steel easily) and vibrant red fluorescence under UV light. Common locations include Myanmar (Burma), Mozambique, Thailand, and Sri Lanka.

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