SciShow Rocks Box: Azurite

Formula: Cu₃(CO₃)₂(OH)₂
Mohs: 3.5 - 4

This stunning blue mineral has been used as a pigment for centuries—and no, it isn’t lapis lazuli. Azurite is a beautiful, deep blue crystal that we’ve coveted for almost as long as we’ve been making art. The color comes from copper, which makes sense, given that it’s a form of weathered copper ores. And azurite is just one step in that chain, because it can turn into malachite, a similar mineral with a bright green hue.

In fine art, azurite has been a big hit with painters all over the world. Medieval European artists used it as a layer underneath more expensive ultramarine paint to get more bang for their buck. And in east Asia, skilled painters could play with the particle size to alter the resulting shade of blue. Plus, azurite even turns up in ancient Egyptian art from time to time!