Guanacoite Locality: El Guanaco Mine, Guanaco (Huanaco) , Santa Catalina , Antofagasta Province , Antofagasta Region , Chile ( Locality at mindat.org ) Picture width 2 mm. Collection and photograph Christian Rewitzer — Photo: Christian Rewitzer · CC BY-SA 3.0
Guanacoite
Guanacoite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Cu₂Mg₃(OH)₄(AsO₄)₂·4H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/c). It is a member of the Akrochordite structural group.
Key properties: Mohs hardness 3; specific gravity 3.29–3.31; White to pale blue streak; Vitreous luster; optically biaxial.
IMA symbol Gnc, IMA status: approved, named in 2003.
A secondary phase in a high sulfidation-type, Au-rich epithermal deposit hosted by felsic rocks (El Guanaco mine), weathered in an arid and Mg-rich environment.
It is found associated with Arhbarite, conichalcite, olivenite, chrysocolla, brochantite, quartz, enargite (Chile); quartz, dolomite, chalcopyrite, chromite, cuprite, malachite.
The name refers to the occurrence at El Guanaco mine, Chile.