Beautiful Blue Arhbarite Crystals From Chile Minerals 9:03 PM A+ A- Print Email Photo: Christian Rewitzer Arhbarite Formula: Cu2Mg(AsO4)(OH)3Colour: Dark blue to medium blueLustre: Sub-Vitreous, WaxyCrystal System: Triclinic From: El Guanaco Mine, Guanaco (Huanaco), Santa Catalina, Antofagasta Province, Antofagasta Region, Chile.