Malachite (& Azurite) (Carbonate)Cu2CO3(OH)2
Hardness: 3.5 - 4.0
Specific Gravity: 3.7 - 4.0
Characteristics: Malachite is green, often earthy; sometimes occurs as crystals with adamantine or vitreous luster; may occur as agate-like concentrations; effervesces in HCl; copper in mineral produces green flame. Azurite has similar characteristics but is blue and is not as common as malachite.
Found in oxidized copper deposits, on weathered pennies and copper statues as a green stain. An associated mineral is azurite, shown in the lower picture to the right, which has a very similar chemical composition.
Uses of malachite include as a valuable ornamental stone and as a minor ore of copper.
(Primary text: Perkins, D. 2002. Mineralogy. Prentice Hall.)