Formula: K3Cu2+20Al3Si29O76(OH)16.8H2O
Unclassified silicate
Specific gravity: 2.96
Streak: Greenish white
Colour: Bluish green
Solubility: Readily decomposed by acids such as hydrochloric and nitric leaving a coherent white mass of hydrated silica (AM43.1107).

Hydrothermal environments

Ajoite is a secondary copper mineral that occurs in oxidised copper-rich deposits (HOM). It is found in massive fracture coatings, vein fillings, vugs, associated with shattuckite, quartz, muscovite variety sericite and pyrite (Dana).

At Munihuaza, Mexico, ajoite is associated with shattuckite, mottramite variety duhamelite and sillénite (HOM).

At Messina, South Africa, ajoite is found as inclusions in quartz and associated with quartz and papagoite (HOM).

At the Potter-Cramer property, Maricopa County, Arizona, USA, ajoite is associated with creaseyite and fluorite (HOM).

At the type locality, the New Cornelia Mine, Ajo, Pima County, Arizona, USA, ahoite is associated with shattuckite, quartz, pyrite, muscovite and conichalcite (Mindat).


Ajoite may form as an alteration product of shattuckite, and also it may itself alter to shattuckite.

Common impurities: Fe,Mn,Ca

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