Guanacoite

guanacoite

arhbarite

conichalcite

enargite

Images

Formula: MgCu₂Mg₂(AsO₄)₂(OH)₄(H₂O)₄
Arsenate, akrochordite group
Crystal System: Monoclinic
Specific gravity: 3.31 measured, 3.36 calculated for the ideal formula
Hardness: 3
Streak: White to pale blue
Colour: Blue to pale blue
Environments

Hydrothermal environments

Localities

At the type locality, the Guanaco Project, Taltal, Antofagasta Province, Antofagasta, Chile, guanacoite occurs as blue to pale blue prismatic to acicular crystals up to 0.7 mm in length, in association with arhbarite, conichalcite, olivenite, chrysocolla, brochantite, quartz and enargite (EJM 18.6.813-821.
It is a secondary phase in a high sulphidation-type, gold-rich epithermal deposit hosted by felsic rocks, weathered in an arid and magnesium-rich environment (HOM).

At the Taghouni Mine, Ouisselsate Caïdat, Amerzgane Cercle, Ouarzazate Province, Drâa-Tafilalet Region, Morocco, guanacoite is associated with quartz, dolomite, chalcopyrite, chromite, cuprite, malachite and agardite-(Ce) (EJM 18.6.813-821.

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