mineral

Blue Sapphire (Tumbled/Polished)

Corundum (Al2O3)

Hardness: 9 on the Mohs scale. Color: Deep blue due to trace amounts of iron and titanium. Luster: Vitreous to Adamantine. Crystal structure: Trigonal/Hexagonal. Cleavage: None (has parting). Specific gravity: 3.98-4.06.

Hardness: 9 on the Mohs scale
Color: Deep blue due to trace amounts of iron and titanium
Luster: Vitreous to Adamantine

Identified April 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed in aluminum-rich metamorphic rocks (such as marble or gneiss) or in igneous rocks like syenite. They are often found in secondary alluvial deposits where they have been weathered from their primary host rock.

Uses & applications

Primary use is in high-end jewelry (faceted or cabochons). Industrial uses include watch crystals, high-durability windows, and abrasive compounds due to extreme hardness.

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 except red (red corundum is classified as Ruby).

Field identification & locations

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