Mineral · Diaspore group
Goethite
α-Fe3+O(OH)
Goethite is the iron oxyhydroxide behind most 'limonite' and rust, forming velvety botryoidal crusts and radiating needles at Colorado's Pikes Peak (with amazonite), Cornwall and Morocco. The yellow-brown streak distinguishes it from hematite. Iridescent 'turgite' from Graves Mountain, Georgia, is goethite-hematite with a thin-film tarnish.
| Formula | α-Fe3+O(OH) |
|---|---|
| IMA status | grandfathered |
| Crystal system | Orthorhombic |
| Mohs hardness | 5–5.5 |
| Group | Diaspore group |
| Type locality | Hollertszug Mine, Herdorf, Germany |
| Streak | Yellowish brown |
| Specific gravity | 4.3 |
| Reference list | IMA List of Minerals (RRUFF) — verify formula and status against the current list |
Elsewhere
Cite this article
Stratum Study. "Goethite" (Mineral). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/minerals/goethite. Accessed 2026-09-20.
@misc{stratum-goethite,
title = {Goethite},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/minerals/goethite}},
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.