mineral
Corundum (Sapphire in Matrix)
Aluminum Oxide (Al2O3)
AI-generated identification · may be incorrectHardness of 9 on the Mohs scale, hexagonal crystal system, vitreous to adamantine luster, uneven to conchoidal fracture, specific gravity of 4.0
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Physical properties
Hardness of 9 on the Mohs scale, hexagonal crystal system, vitreous to adamantine luster, uneven to conchoidal fracture, specific gravity of 4.0
Formation & geological history
Formed in metamorphic or igneous rocks such as marble, pegmatites, or basaltic alluvial deposits through high-pressure and high-temperature geological processes
Uses & applications
Used in high-end jewelry, industrial abrasives, watch bearings, and laser components
Geological facts
Corundum is the second hardest natural mineral on Earth, surpassed only by diamond. Gem-quality red varieties are called rubies, while all other colors are called sapphires.
Field identification & locations
Identified by its exceptional hardness, heavy weight for its size, and barrel-shaped hexagonal crystal habit. Found worldwide, particularly in Sri Lanka, Madagascar, East Africa, and parts of the USA.
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Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous
Septarian Pebble
Septarian nodule / Concretion
sedimentary