Ceruleite: Gemstone Information
Opaque turquoise-blue ceruleite (Cu2Al7(AsO4)4(OH)1312H2O) is found in the gold mine Emma Luisa, Guanaco District, Antofagasta, Chile and at an unspecified locality in Bolivia. The triclinic material occurs as earthy masses which nonetheless take a reasonable polish. The hardness is 5–6, SG 2.70–2.80 and mean RI 1.60. Specimens have been resin-stabilized. Ceruleite occurs in the oxidized zone of arsenic-rich polymetallic mineral deposits.