09/03/2021
From our personal collection.
This specimen is Azurite & Malachite on it matrix. One would find the 2 minerals together quite often.
MALACHITE:
Malachite is a green copper carbonate hydroxide mineral with a chemical composition of Cu2(CO3)
Malachite is a mineral that forms at shallow depths within the Earth, in the oxidizing zone above copper deposits. It precipitates from descending solutions in fractures, caverns, cavities, and the intergranular spaces of porous rock. It often forms within limestone where a subsurface chemical environment favorable for the formation of carbonate minerals can occur. Associated minerals include Azurite, Bornite, Calcite, Chalcopyrite, Copper, Cuprite, and a variety of iron oxides.
AZURITE:
Azurite is a copper carbonate hydroxide mineral with a chemical composition of Cu3(CO3)2(OH)2.
Azurite is a secondary mineral that usually forms when carbon-dioxide-laden waters descend into the Earth and react with subsurface copper ores. The carbonic acid of these waters dissolves small amounts of copper from the ore. The dissolved copper is transported with the water until it reaches a new geochemical environment. This new environment could be a location where water chemistry or temperature changes, or where evaporation occurs. If conditions are right, the mineral azurite might form. If these conditions persist for a long time, a significant accumulation of azurite might develop. This has occurred in many parts of the world.
Azurite precipitation occurs in pore spaces, fractures, and cavities of the subsurface rock. The resulting azurite is usually massive or nodular. In rare situations, azurite is found as stalactitic and botryoidal growths. Well-formed monoclinic crystals are infrequently found. These can only occur if azurite precipitates unrestricted in a fracture or cavity and is not disrupted by later crystallization or rock movements.
