Commonly encountered compounds are copper(II) salts, which often impart blue or green colors to such minerals as azurite, malachite, and turquoise, and have been used widely and historically as pigments.
cOMMonlY encoUntERed cOmpoundS are cOPpeR(II) salts, whiCh OFteN impart blue or GReen ColoRS to such miNERalS As AZUrIte, maLAchite, aNd turquoiSe, AnD have bEEn useD wiDely ANd HistOricaLly As PigmeNTs.