mineral
Corundum (Sapphire and Ruby)
Aluminum Oxide (Al2O3)
Hardness: 9 on the Mohs scale. Color: Blue (Sapphire) and Red (Ruby). Luster: Adamantine to Vitreous. Crystal Structure: Hexagonal/Trigonal. Specific Gravity: 3.95-4.10.
- Hardness
- 9 on the Mohs scale
- Color
- Blue (Sapphire) and Red (Ruby)
- Luster
- Adamantine to Vitreous
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Physical properties
Hardness: 9 on the Mohs scale. Color: Blue (Sapphire) and Red (Ruby). Luster: Adamantine to Vitreous. Crystal Structure: Hexagonal/Trigonal. Specific Gravity: 3.95-4.10.
Formation & geological history
Formed in aluminum-rich metamorphic rocks (schist, gneiss) or igneous rocks (nepheline syenite, pegmatite). Often found in alluvial deposits (river sands).
Uses & applications
Primarily used as high-end gemstones in jewelry. Industrial-grade corundum is used as an abrasive (emery) and in scratch-resistant windows or lasers.
Geological facts
Sapphire and Ruby are both variations of the mineral Corundum; the red color in rubies comes from Chromium, while sapphires get blue from Iron and Titanium.
Field identification & locations
Identified by extreme hardness (scratches almost everything except diamond). Commonly found in Myanmar, Sri Lanka, Madagascar, and Thailand. Look for hexagonal barrel-shaped crystals.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
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](https://media.rockidentification.com/2391a63f-fb20-47d5-af9a-2035851eb32e-thumbnail.jpg)
Green Apatite on Albite
Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]
mineral