Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. Azurite was used as a blue pigment for centuries. Depending on the degree of fineness to which it was ground, and its basic content of copper carbonate, it gave a wide range of blues.
Azurite is soft, with a Mohs hardness of only 3.5 to 4. The specific gravity of azurite is 3.77 to 3.89 it is often pseudomorphically replaced by malachite which is why we commonly see the two together.