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Gold
Gold occurs in in many parts of the South Island. Most West Coast gold comes from glacial and alluvial deposits where it is found as grains within river sand and gravel. Exploration in recent years has identified significant resources. Total in-ground placer gold resources for the region have been roughly estimated at 300 tonnes.
Most of the gold deposits in the South Island were first formed by erosion from glaciers over millions of years, then the rivers carried the gold further and deposited it downstream and along coastal margins along beaches and offshore. While the rocks that are the source of the gold may contain only very small amounts of the metal, this erosion and natural reworking over long periods of time has trapped and concentrated the heavy mineral grains. Over time the gold-bearing rock is eroded and water deposits the gold downstream. Gold is very heavy, and so is deposited in places where the current slows down, on bends, and in depressions in the river bed. These are called alluvial or placer deposits, or placer gold.
Alluvial gold is relatively easy to extract from its surroundings as the hard work has already been done over time by natural forces. No chemical processes are required.
On the West Coast a number of comparatively small operations mine alluvial gold deposits. Bulldozers and excavators strip away the topsoil and stockpile this. The alluvial deposits are mined before the area is recontoured and the topsoil replaced.
On the Grey River a gold dredge completes the same operation, leaving behind new productive pasture.
On the region's beaches blacksanders use a variety of methods to extract gold from the black beach sands.These are small, often part time, one or two person operations.
Off the coast exploration work has started on the gold-bearing sediment washed onto the continental shelf by glacial action and river outwash.
There is hard rock gold mining on the Coast too.
OceanaGold's Globe Progress open pit mine near Reefton commenced production in 2007.
Rehabilitation is an integral part of all modern gold mining and is part of the operation right from the start.
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