Mineral · Spinel group
Spinel
MgAl2O4
Spinel is magnesium aluminium oxide, forming sharp octahedra in red, pink, blue and black in marble at Mogok (Myanmar), Luc Yen (Vietnam), Mahenge (Tanzania) and Sri Lanka, and black octahedra at Amity, New York. The 'Black Prince's Ruby' is a spinel. Octahedral habit and hardness 8 distinguish it from garnet and corundum.
| Formula | MgAl2O4 |
|---|---|
| IMA status | grandfathered |
| Crystal system | Cubic |
| Mohs hardness | 7.5–8 |
| Group | Spinel group |
| Type locality | None |
| Streak | White |
| Specific gravity | 3.6 |
| Reference list | IMA List of Minerals (RRUFF) — verify formula and status against the current list |
Fakes and treatments
Synthetic spinel is common in jewellery; specimen octahedra in marble are usually natural but sometimes reglued.
Elsewhere
Cite this article
Stratum Study. "Spinel" (Mineral). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/minerals/spinel. Accessed 2026-09-20.
@misc{stratum-spinel,
title = {Spinel},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/minerals/spinel}},
year = {2026},
note = {Mineral article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, wikidata, commons. Accessed 2026-09-20.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.