mineral

Rough Green Sapphire (Corundum)

Corundum (Al2O3 - Aluminum Oxide with trace elements)

Hardness: 9 on Mohs scale. Color: Olive to forest green. Luster: Adamantine to vitreous. Crystal structure: Trigonal/Hexagonal. Cleavage: None (has basal parting). Specific gravity: 3.98-4.06.

Hardness: 9 on Mohs scale
Color: Olive to forest green
Luster: Adamantine to vitreous

Identified March 24, 2026More mineral →

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Physical properties

Hardness: 9 on Mohs scale. Color: Olive to forest green. Luster: Adamantine to vitreous. Crystal structure: Trigonal/Hexagonal. Cleavage: None (has basal parting). Specific gravity: 3.98-4.06.

Formation & geological history

Formed in metamorphic environments like marble or schists, and igneous settings such as basalt-related deposits. They are often found in alluvial placer deposits where the heavy minerals concentrate after erosion.

Uses & applications

Used primarily in jewelry as a gemstone. In industrial forms, non-gem quality corundum is used for abrasives (emery), watch bearings, and scratch-resistant glass (sapphire crystal).

Geological facts

Sapphires are the second hardest natural mineral on Earth after diamonds. While blue is most famous, 'Green Sapphire' gets its color from iron trace elements in the crystal lattice.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by steel or quartz) and high density/heaviness for its size. Common locations include Montana (USA), Australia, Sri Lanka, and Thailand.

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