Azurite (Cu3(OH)2(CO3)2, copper basic carbonate) from Artés. Azurite produces different kinds of crystals of the monolithic system, but it is commonly found as patinas or reniform or powdery masses. Usually, azurite and malachite are found together, but azurite can turn into malachite by chemical alteration. Azurite has a beautiful Indian blue color, blue streak and 3,5-4 hardness degree. Azurite is a secondary source of copper and it is used as an ornamental stone too. Although less abundant than malachite, azurite is found in Sallent and Artés, in the so-called red-bed copper mineralization (see malachite) that are located at the bottom of paleochannels (ancient riverbeds) in Artés geological formation.
[photo Joaquim Sanz / Museum of Geology Valentí Masachs]