Azurite is an alkaline copper carbonate. It is a product of the oxidation of copper sulphides in the oxidation zones of copper deposits in carbonate rocks. Tabular, columnar, prismatic crystals, stalactites, concretions predominate. Tiny crystals form integral aggregates. Hardness 3.5 to 4. It is often found in combination with malachite (to which it is converted by oxidation over time), chrysocolla, cuprite, cerusite, smithsonite and other minerals. Thanks to its beautiful blue color, it is very popular among collectors. It is used in jewelry (most often in the form of cabochons) and is also used to make blue dye.