mineral
Rough Sapphire (possibly Yellow/Green Corundum)
Corundum (Al2O3)
Hexagonal crystal system, hardness 9 on Mohs scale, vitreous to adamantine luster, no cleavage, specific gravity 3.98-4.06, pale yellow-green color with internal fractures.
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Physical properties
Hexagonal crystal system, hardness 9 on Mohs scale, vitreous to adamantine luster, no cleavage, specific gravity 3.98-4.06, pale yellow-green color with internal fractures.
Formation & geological history
Formed in aluminum-rich metamorphic rocks (schists, gneisses) or igneous rocks like syenite. Often found as water-worn pebbles in alluvial deposits (gem gravels).
Uses & applications
Abrasives (industrial grade) or faceted as gemstones for jewelry (gem grade). High-quality stones are valuable to collectors.
Geological facts
Corundum is the second hardest natural mineral after diamond. When it is red, it is called ruby; every other color is called sapphire. Common sapphire often appears in pale, muddy tones like this specimen.
Field identification & locations
Identified by its extreme hardness (cannot be scratched by quartz or steel) and high density. Commonly found in Sri Lanka, Madagascar, and East Africa in riverbeds.
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Epidote
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