mineral

Sapphire (Rough)

Corundum (Al2O3)

Hardness: 9 on the Mohs scale. Color: Deep blue. Luster: Vitreous to sub-adamantine. Crystal structure: Trigonal/Hexagonal. Cleavage: None (has parting). Specific gravity: 3.95-4.10.

Hardness: 9 on the Mohs scale
Color: Deep blue
Luster: Vitreous to sub-adamantine

Identified July 5, 2026More mineral →

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Physical properties

Hardness: 9 on the Mohs scale. Color: Deep blue. Luster: Vitreous to sub-adamantine. Crystal structure: Trigonal/Hexagonal. Cleavage: None (has parting). Specific gravity: 3.95-4.10.

Formation & geological history

Formed in aluminum-rich metamorphic rocks (schists, gneisses) and igneous rocks (syenites, pegmatites) under high pressure and temperature. Commonly found in alluvial deposits.

Uses & applications

Primarily used in jewelry as a precious gemstone. Industrial uses include infrared optical components, high-durability windows, and watch crystals.

Geological facts

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

Field identification & locations

Identify by its extreme hardness (will scratch almost any other mineral) and its weight for its size. Look for hexagonal barrel-shaped crystal habits in the field. Found in Sri Lanka, Madagascar, Australia, and Montana, USA.