AZURITE on LIMONITE (cabinet)

Azurite has the chemical formula Cu3(CO3)2(OH)2, with copper(II) cations bonded to both carbonate and hydroxide anions. It is one of two relatively common basic copper(II) carbonate minerals, the other being the bright green malachite. Aurichalcite, on the other hand, is a rare basic carbonate mineral containing copper and zinc. Simple copper carbonate (CuCO3) is not found in nature due to the strong affinity of the Cu2+ ion for the hydroxide anion HO−.

Limonite is an iron ore made up of a blend of hydrated iron(III) oxide-hydroxides with varying compositions. While it is often represented by the formula FeO(OH)·nH2O, this depiction is somewhat misleading since the proportions of oxide to hydroxide can differ significantly.