mineral

Blue Sapphire

Corundum (Al2O3)

Hardness: 9 on Mohs scale; Color: Deep blue (due to iron and titanium traces); Luster: Vitreous/Glassy; Crystal System: Trigonal (Hexagonal); Cleavage: None/Parting; Specific Gravity: 3.95–4.03.

Hardness: 9 on Mohs scale
Color: Deep blue (due to iron and titanium traces)
Luster: Vitreous/Glassy

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 Mohs scale; Color: Deep blue (due to iron and titanium traces); Luster: Vitreous/Glassy; Crystal System: Trigonal (Hexagonal); Cleavage: None/Parting; Specific Gravity: 3.95–4.03.

Formation & geological history

Formed in metamorphic or igneous environments, particularly in marble, basalt, or pegmatites. It forms under high pressure and temperature deep within the Earth's crust over millions of years.

Uses & applications

Primary use is in high-end jewelry (one of the 'big four' gemstones). Industrial-grade sapphire is used for watch crystals, electronics, and scratch-resistant windows.

Geological facts

Sapphire is the second hardest natural substance on Earth after diamond. While blue is most famous, sapphires occur in every color except red (which is classified as ruby).

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by steel or quartz) and high density. Commonly found in river deposits (alluvial) in Sri Lanka, Madagascar, Myanmar, and Montana, USA.