mineral

Ruby (Raw/Rough)

Corundum (Al2O3 with Chromium trace)

Hardness: 9 on Mohs scale; Color: Pinkish-red to deep violet-red; Luster: Adamantine to vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (parting sometimes present); Specific gravity: 3.97–4.05

Hardness: 9 on Mohs scale
Color: Pinkish-red to deep violet-red
Luster: Adamantine to vitreous

Identified April 14, 2026More mineral →

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Physical properties

Formation & geological history

Formed through contact metamorphism or in igneous rocks like basalt. Found in marble-hosted environments or gravel-rich alluvial deposits. Rubies range in age from hundreds of millions to billions of years old depending on the source deposit.

Uses & applications

Primarily used in high-end jewelry and as a gemstone for collectors. Industrial grade corundum is used for abrasives, lasers, and watch bearings.

Geological facts

The red color is caused specifically by the presence of chromium. Without chromium, the mineral is simply called sapphire. It is the second hardest natural substance on Earth after diamond.

Field identification & locations

Identify in the field by its extreme hardness (scratching anything but diamond), its dense weight, and its fluorescent glow under UV light. Commonly found in Myanmar, Sri Lanka, Thailand, and Mozambique.

Other mineral specimens

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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