Spinel
Species
Rare · MgAl₂O₄
Magnesium aluminium oxide forming octahedral crystals in metamorphic marbles and igneous rocks. Long confused with ruby because of its similar red colour and shared gem gravels: several famous 'rubies', such as the Timur Ruby, are spinels.
Identity
- Formula
- MgAl₂O₄
- Chemical class
- Oxide
- Mineral group
- Chromite, Magnetite
- Also known as
- Balas ruby (archaic red spinel), Pleonaste (dark variety)
Crystallography
- Crystal system
- Cubic
- Habits
- Octahedral, Massive
- Fracture
- Conchoidal
Physical properties
- Mohs hardness
- 8
- Density
- 3.58 g/cm³
- Luster
- Vitreous
- Colors
- red, pink, blue, purple, black, colorless, orange
- Streak
- white
- Transparency
- Transparent, Translucent
Geology
- Origins
- Metamorphic, Igneous
- Host rocks
- Volcanic rock, Ultramafic rock (peridotite, serpentinite), Schist and gneiss, Marble
- Associated minerals
- Corundum, Olivine, Mica, chondrodite, Scapolite
- Found in
- Kimberlite
- Geography
- Myanmar, Sri Lanka, Tajikistan, Vietnam, Tanzania
Classification
- Rarity
- Rare
- Gem quality
- Yes
Sources
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Spinel. Mineralogical Society of America, Handbook of Mineralogy, 2021.
- Spinel. Mindat.org (Hudson Institute of Mineralogy).
- Spinel. Gemdat.org (Hudson Institute of Mineralogy).
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