* Metamorphic rocks: Spinel is a common mineral in metamorphic rocks, especially those formed under high pressure and temperature conditions. These include:
* Marble: Spinel forms within marble when limestone is metamorphosed.
* Schist and gneiss: Spinel can be found in these foliated metamorphic rocks, often associated with other minerals like garnet, corundum, and pyroxene.
* Magmatic rocks: Spinel can also crystallize from magma, especially in:
* Ultramafic rocks: These are rocks rich in magnesium and iron, like peridotite and dunite, where spinel is a common constituent.
* Basalt and gabbro: Spinel can be found in these mafic rocks, though it is less abundant than in ultramafic rocks.
* Skarn deposits: Skarn deposits are formed when hot fluids interact with existing rocks, often creating new minerals. Spinel can form in these deposits, usually associated with other minerals like garnet, pyroxene, and magnetite.
* Gemstones: Spinel can also form in gem deposits, often found in alluvial gravels and placer deposits.
Specific locations where spinel is found:
* Myanmar (Burma): Known for its high-quality red spinel.
* Afghanistan: Produces a variety of spinel colors, including red, pink, and blue.
* Sri Lanka: Famous for its star spinel.
* Tanzania: Produces a variety of spinel colors, including pink, purple, and green.
* Madagascar: Produces a variety of spinel colors, including blue, purple, and pink.
* Vietnam: Produces a variety of spinel colors, including red, pink, and blue.
* United States: Spinel has been found in several states, including California, Montana, and New York.
The specific formation conditions and location of spinel deposits can vary significantly, influencing the color, clarity, and size of the gemstones.
