2CuCO3-Cu(OH)2 . A deep blue mineral composed of basic copper carbonate that is naturally found with the green copper carbonate mineral called malachite. Azurite and malachite have been used as gemstones and paint pigments since before 3000 BCE. They are prepared as pigments by careful selection, grinding, washing and levigation. Coarsely ground azurite gives a deep blue colour while finely ground particles give a lighter more transparent tone. Azurite is lightfast but is sensitive to acids and sulphur fumes. Basic copper carbonate can also be made artificially by colouring chalk with copper sulphate. The synthetic pigment, called blue verditer, blue bice, Bremen blue or ashes blue, tends to have regularly sized particles with rounded edges. The colour is similar to finely ground azurite. It is listed among the pigments used for colouring stucco marble in the nineteenth and twentieth century. Synonyms: blue verditer; mountain blue; Pigment Blue 30; CI 77420; ashes blue; Bremen blue; blue bice; Armenian stone; lapis armenius; chessylite; blue malachite; mineral blue; basic copper carbonate; basic cupric carbonate; copper blue; chessy copper; bleu d'Allemagne (Fr.); Bergblau (Ger.); Bergasur; Azurit (Ger.); azurite (Fr.); azzurrite (It.); azzurro della magna (It.); azurita (Sp.); azurium citramarinum. Wittenburg (1999); Museum of Fine Arts, Boston (2000). [J. Cassar, R. de Angelis]