Formula: K3Cu2+20Al3Si29O76(OH)16.8H2O
Unclassified silicate
Crystal System: Triclinic
Specific gravity: 2.96 measured, 2.951 calculated
Streak: Greenish white
Colour: Bluish green
Solubility: Readily decomposed by acids such as hydrochloric acid and nitric acid leaving a coherent white mass of hydrated silica (AM43.1107).
Common impurities: Fe,Mn,Ca

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, most of the ajoite is compact massive and is intimately mixed with dark blue shattuckite and white massive quartz. Occasional small cavities contain aggregates of elonaged plates of ajoite, a millimeter and less in length. Other less abundant associated minerals observed are minute pearly scales of sericite, white powdery quartz, pyrite, very pale blue altering shattuckite, limonitic stains, and on one specimen massive conichalcite (AM 43.1107-1111).


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

Back to Minerals