mineral

Ruby (Corundum)

Aluminum oxide (Al2O3) with Chromium traces

Hardness: 9.0 on Mohs scale; Color: Red to pinkish-red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Specific Gravity: 3.97-4.05

Hardness: 9
Color: Red to pinkish-red
Luster: Vitreous to sub-adamantine

Identified June 1, 2026More mineral →

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Physical properties

Hardness: 9.0 on Mohs scale; Color: Red to pinkish-red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Specific Gravity: 3.97-4.05

Formation & geological history

Formed in metamorphic rocks (schists/gneisses) or marble through contact metamorphism, or found in alluvial deposits. They often form in alumina-rich and silica-poor environments.

Uses & applications

Primarily used in high-end jewelry, luxury goods, and historically as a watch-bearing material. Industrial-grade synthetic rubies are used in lasers and high-precision instruments.

Geological facts

The red color is caused by the presence of chromium. Natural rubies often contain 'silk' (rutile inclusions), while flawless large rubies are rarer than diamonds of similar size.

Field identification & locations

Identify by extreme hardness (scratches almost anything but diamond), distinct pleochroism, and UV fluorescence. Major sources include Myanmar (Burma), Madagascar, 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

Biotite Schist

Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]

metamorphic