Malachite

Malachite is a copper carbonate mineral. This green-coloured mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses. Individual crystals are rare but do occur as slender to acicular prisms. Pseudomorphs after more tabular or blocky azurite crystals also occur.

Occurence
Malachite often results from weathering of copper ores and is often found together with azurite, goethite, and calcite. Except for its vibrant green colour, the properties of Malachite are similar to those of azurite and aggregates of the two minerals occur frequently together. Malachite is more common to azurite and is typically associated with copper deposits around limestones, the source of the carbonate.

Source

 * http://en.wikipedia.org