mineral

Ruby

Corundum (Al2O3)

Hardness: 9 on Mohs scale; Color: Pinkish-red to pigeon-blood red; Luster: Adamantine to vitreous; Crystal Structure: Trigonal (hexagonal prisms); Cleavage: None (has parting); Specific Gravity: 3.97-4.05

Hardness: 9 on Mohs scale
Color: Pinkish-red to pigeon-blood red
Luster: Adamantine to vitreous

Identified June 18, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed in metamorphic environments like marble or schist, and sometimes in igneous rocks like basalt. Created through high pressure and heat during tectonic events. Inclusion of chromium provides the red color.

Uses & applications

Primary use is in high-end jewelry (gemstones). Industrial uses include lasers, precision bearings in watches, and specialized medical instruments due to extreme hardness.

Geological facts

Ruby is the red variety of the mineral corundum; all other colors are sapphires. It is one of the four traditional 'precious' stones. Chromium is the trace element that gives it both its red color and its fluorescence.

Field identification & locations

Identify in the field by its extreme hardness (scratches glass and most other minerals), hexagonal crystal habit, and distinct red color. Commonly found in Myanmar (Burma), Madagascar, Thailand, and Mozambique.