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