mineral

Ruby

Corundum (Aluminum Oxide with Chromium), Al2O3:Cr

Hardness: 9 on Mohs scale; Color: Red (pigeon blood to pinkish-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 (pigeon blood to pinkish-red)
Luster: Vitreous to sub-adamantine

Identified May 2, 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 rocks such as marble and schist, or in igneous rocks like basalt. Created through high pressure and temperature where aluminum thrives and silica is scarce. Most deposits are millions of years old.

Uses & applications

Primarily used in high-end jewelry (faceted or cabochon), and industrially in lasers, watchmaking (jeweled movements), and precision instruments.

Geological facts

The red color is caused by trace amounts of chromium. It is the birthstone for July and is the second hardest natural mineral after diamond. Some rubies exhibit asterism, creating a 6-rayed star.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by steel or quartz) and distinct red fluorescence under UV light. Commonly found in Myanmar (Burma), Madagascar, Thailand, and Mozambique.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

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