mineral
Spinel
Magnesium Aluminum Oxide (MgAl2O4)
Hardness: 8.0 on Mohs scale; Color: Pink, magenta; Luster: Vitreous (glassy); Crystal structure: Isometric (octahedral); Cleavage: Indistinct; Specific gravity: 3.54-3.63
- Hardness
- 8
- Color
- Pink, magenta
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 8.0 on Mohs scale; Color: Pink, magenta; Luster: Vitreous (glassy); Crystal structure: Isometric (octahedral); Cleavage: Indistinct; Specific gravity: 3.54-3.63
Formation & geological history
Formed through regional metamorphism of limestone and dolostone, or as a primary mineral in mafic igneous rocks. It is most frequently found in magnesium-rich marbles.
Uses & applications
Primarily used as a gemstone in jewelry due to its hardness and brilliance. Synthetic spinel is used in refractories and as a blue-colored glass substitute.
Geological facts
Historically mistaken for ruby because they are found in the same mines; the 'Black Prince's Ruby' in the British Imperial State Crown is actually a red spinel.
Field identification & locations
Identify by its octahedral (double pyramid) crystal habit and extreme hardness. Common locations include Myanmar (Mogok), Sri Lanka, Vietnam, and Tajikistan.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
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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
Epidote
Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)
mineral