Formula: (Zn,Al)3(Si,Al)2O5(OH)4
Phyllosilicate (sheet silicate), serpentine group, forms a solid solution with berthierite
Specific gravity: 3.08 to 3.10
Hardness: 3½ to 4
Streak: White, pale green
Colour: Yellowish white to bluish
Solubility: Dissolves completely in nitric acid, 10% hydrochloric acid and 30% solution of NaOH, gelatinises upon evaporation, fuses easily to a white enamel (Dana)
Common impurities: Fe,Cu,Mg,Ca,K

Hydrothermal environments

Fraipontite is a low-temperature clay mineral found with secondary zinc and copper minerals in oxidised deposits, often associated with sauconite. It forms pseudomorphs after azurite, cuprite and other minerals, and is an alteration product of smithsonite (Dana, Webmin).


There are three co-type Localities:
The Altenberg mine, Kelmis, Liège, Wallonia, Belgium
The Akdzhal deposit, Akdzhal, Zharma, East Kazakhstan, Kazakhstan
The Sterling mine, Sterling Hill, Ogdensburg, Franklin Mining District, Sussex County, New Jersey, USA
Fraipontite occurs there as crusts of fibres 4-10 mm thick on smithsonite (Mindat).

At the Altenberg mine, Kelmis, Liège, Wallonia, Belgium, fraipontite is associated with smithsonite (HOM).

At Moresnet, Plombières (Blieberg; Bleiberg; Bleyberg), Liège, Wallonia, Belgium, fraipontite is found on smithsonite (Dana).

At the Tsumeb mine, Tsumeb, Oshikoto Region, Namibia, fraipontite is associated with gebhardite, willemite and cerussite (HOM).

At Kap-Kutan Cave System, Kugitangtau Ridge, South Tien-Shan Mountains, Lebap, Turkmenistan, fraipontite is found coating fluorite, associated with gypsum, jarosite and quartz (Dana).

At the Silver Bill Mine, Costello Mine group, Gleeson, Turquoise Mining District, Cochise County, Arizona, USA, fraipontite is associated with sauconite (HOM).

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