Mineral · Nesosilicates
Staurolite
Fe2+2Al9Si4O23(OH)
Staurolite is the brown iron aluminium silicate of schists that forms cruciform twins, the 'fairy crosses' of Fannin County (Georgia, state mineral), Taos (New Mexico) and Brittany, and large single crystals in Russia and Switzerland. Genuine twins are rough-surfaced and slightly irregular; smoothly carved 'staurolite crosses' sold as souvenirs are cut from massive rock.
| Formula | Fe2+2Al9Si4O23(OH) |
|---|---|
| IMA status | grandfathered |
| Crystal system | Monoclinic |
| Mohs hardness | 7–7.5 |
| Group | Nesosilicates |
| Type locality | None |
| Streak | White |
| Specific gravity | 3.7 |
| Reference list | IMA List of Minerals (RRUFF) — verify formula and status against the current list |
Fakes and treatments
Carved and reshaped 'fairy crosses' are widespread; natural twins show pitted faces and mica inclusions.
Elsewhere
Cite this article
Stratum Study. "Staurolite" (Mineral). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/minerals/staurolite. Accessed 2026-09-20.
@misc{stratum-staurolite,
title = {Staurolite},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/minerals/staurolite}},
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.