Mineral · Turquoise group
Turquoise
Cu(Al,Fe3+)6(PO4)4(OH)8·4H2O
Turquoise is a hydrated copper aluminium phosphate, the sky-blue to green gem of the American Southwest (Sleeping Beauty, Kingman, Bisbee, Morenci), Iran and China. Natural, untreated high-grade turquoise is rare and most rough is stabilised with resin; crystallised turquoise from Lynch Station, Virginia, is the collector's specimen. Spiderweb matrix patterns and mine of origin drive value.
| Formula | Cu(Al,Fe3+)6(PO4)4(OH)8·4H2O |
|---|---|
| IMA status | grandfathered |
| Crystal system | Triclinic |
| Mohs hardness | 5–6 |
| Group | Turquoise group |
| Type locality | Nishapur, Iran (historical) |
| Streak | White to pale green |
| Specific gravity | 2.6–2.9 |
| Reference list | IMA List of Minerals (RRUFF) — verify formula and status against the current list |
Fakes and treatments
Stabilised, dyed, 'block' (reconstituted powder in resin) and imitation (dyed howlite, magnesite, plastic) turquoise dominate the market; a hot needle on the back reveals resin, and acetone lifts dye from howlite.
Elsewhere
Cite this article
Stratum Study. "Turquoise" (Mineral). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/minerals/turquoise. Accessed 2026-09-20.
@misc{stratum-turquoise,
title = {Turquoise},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/minerals/turquoise}},
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.