mineral

Ruby

Corundum (Al2O3 with Chromium trace elements)

Hardness: 9 on Mohs scale; Color: Red (ranging from orangey-red to purplish-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: Red (ranging from orangey-red to purplish-red)
Luster: Vitreous to sub-adamantine

Identified January 8, 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 through contact or regional metamorphism of aluminum-rich rocks and marbles. Most famous deposits are found in marble-hosted environments like the Mogok Valley in Myanmar (Burma), as well as in basalt-hosted or alluvial deposits.

Uses & applications

Primarily used as a high-value gemstone in fine jewelry. Industrial-grade synthetic rubies are used in lasers, watch bearings (jeweled movements), and high-pressure scientific equipment.

Geological facts

The red color is caused specifically by the presence of chromium. Without chromium, corundum is known as sapphire. The most valuable color is a deep, vivid red known as 'pigeon's blood'.

Field identification & locations

Identify by its extreme hardness (9), hexagonal crystal habit, and distinct pleochroism. Found in places like Myanmar, Thailand, Sri Lanka, and Madagascar. Collectors look for fluorescence under UV light, which many rubies exhibit due to chromium.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral