Faustite

File:Faustite3322.jpg, Ampang Jaleh, Penjom Mine]]

The IMA-approved mineral faustite{{cite web |title=Faustite |url=https://rruff.info/doclib/hom/faustite.pdf|work=RRUFF Project |publisher=Mineral Data Publishing |access-date=2014-04-08}} is a member of the triclinic turquoise group of hydrous phosphates with the chemical composition

{{chem2|ZnAl6(PO4)4(OH)8*4H2O}}. It is named after the American mineralogist and petrologist Dr. George Tobias Faust, who workes with the U.S. Geological Survey (USGS).{{Mindat |id=1623 |name=Faustite |access-date=2014-04-08}}

Some divalent copper generally replaces the zinc position. Faustite is the zinc-rich analogue of turquoise, having almost four times as much zinc than copper in its crystal structure.{{WebMineral |url=https://webmineral.com/data/Faustite.shtml#.U0M57KLDu2A |title=Faustite Mineral Data |access-date=2014-04-08}} Trivalent (ferric) iron may replace some of the aluminum. Minor amounts of calcium may also be present. It has a hardness of 4.5–5.5 on the Mohs scale of mineral hardness, and aside from having a slightly lower hardness, it may be difficult to distinguish it from turquoise in hand specimens.

Faustite has a blue-green to apple green color in polished cabochons. It may be presented as a turquoise imitation and also be treated with stabilizers for jewelry making.