Minerals from the Oxidised Zone

Colourful and spectacular mineral crystals are rare. Crystal growth needs time, space and a steady supply of chemical ingredients. One place where all this happens is the oxidised zone, where water containing dissolved oxygen and carbon dioxide seeps down through the ground into rocks containing metal sulfide ores, and dissolves them. This creates a rich ‘chemical soup’ that reacts with the surrounding rocks to form an array of different minerals.

One third of all minerals are formed in oxidised zones. They are also indicators of what lies below. When prospectors find minerals in the oxidised zone they know there is a chance of finding a rich ore-body nearby.

Oxidised zones occur throughout the world, but many of the most spectacular ones are in arid regions. Australia has some famous oxidised zones, such as Broken Hill in New South Wales, Dundas in Tasmania and Browns Prospect in the Northern Territory.

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