mineral

Blue Sapphire

Corundum (Al2O3 with trace Titanium and Iron)

Hardness: 9 on the Mohs scale; Color: Deep blue; Luster: Vitreous (glass-like); Crystal structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific gravity: 3.95–4.03.

Hardness: 9 on the Mohs scale
Color: Deep blue
Luster: Vitreous (glass-like)

Identified April 27, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 9 on the Mohs scale; Color: Deep blue; Luster: Vitreous (glass-like); Crystal structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific gravity: 3.95–4.03.

Formation & geological history

Formed in aluminum-rich metamorphic rocks (like marble or schist) or igneous rocks (like syenite) under high pressure and temperature. Commonly found in secondary alluvial deposits (riverbeds).

Uses & applications

Primary use is in high-end jewelry. Industrial uses (synthetic) include scratch-resistant watch crystals, optical components, and electronic substrates.

Geological facts

Sapphire is the birthstone for September and the traditional gift for a 45th wedding anniversary. All non-red gem-quality corundums are called sapphires, though blue is the most famous.

Field identification & locations

Identify in the field by its extreme hardness (scratches glass and steel easily) and hex-barrel crystal shape. Look for intense blue color in river gravels near volcanic or metamorphic contacts.

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