Where is Black Spinel found?
MgAl2O4
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Open the appBlack Spinel occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Black Spinel
Sri Lanka
Known for producing fine quality spinel, including black varieties, often found in alluvial deposits.
Myanmar (Burma)
Mogok region is a classic locality for various spinel colors, including black, from both primary and secondary deposits.
Thailand
Gem-quality spinel, including black, is found in alluvial deposits.
Vietnam
Luc Yen and other areas yield black spinel, often associated with marble and other metamorphic rocks.
Madagascar
Various localities produce black spinel, often in association with other gem minerals.
Tanzania
Several regions, particularly in the Tanga and Morogoro areas, are known for spinel occurrences.
Afghanistan
Historically significant source of spinel, including black varieties.
Brazil
Some occurrences of black spinel have been reported.
United States
Minor occurrences in various states, often in metamorphic terrains (e.g., New York, New Jersey).
Collecting tips
- Check Metamorphic Terrains. Focus on areas with contact metamorphic aureoles around igneous intrusions, especially those involving carbonate rocks (limestones, dolomites) or schists.
- Inspect Mafic/Ultramafic Rocks. Look for black spinel as an accessory mineral in peridotites, serpentinites, and some basalts.
- Explore Placer Deposits. Due to its hardness and resistance to weathering, black spinel often concentrates in alluvial (river) and eluvial (residual) deposits. Pan for heavy minerals in stream beds originating from spinel-bearing source rocks.
- Look for Octahedral Crystals. Black spinel commonly forms distinct octahedral crystals. Identifying this crystal habit is a strong indicator.
- Perform Hardness Test. With a Mohs hardness of 8, black spinel will scratch quartz (7) and feldspar (6-6.5). This helps differentiate it from softer black minerals.
- Observe Luster. Its vitreous to sub-adamantine luster is characteristic and can help distinguish it from duller black minerals.
- Check for Magnetism. While pure MgAl2O4 is non-magnetic, iron-rich varieties (pleonaste, hercynite) can be weakly to moderately magnetic due to the presence of Fe2+ and Fe3+. This can help differentiate it from non-magnetic black minerals like tourmaline or onyx.
Quick Check
- Color:
- Black
- Luster:
- Vitreous to sub-adamantine
- Streak:
- White to grayish white
Explore Black Spinel
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