Golden Rivers: Gold in the mountains
Gold occurs in thin veins of white quartz near the crest of the Southern Alps. The gold is accompanied by pyrite (iron sulphide, fools gold) and arsenopyrite ( iron arsenic sulphide). These minerals were left in fractures in the rock as hot water (over 200 degrees C) made its way towards the surface from beneath the Southern Alps. Hot water rises continuously and flows out at the surface in many places, such as the hot springs in the Copeland Valley. As the mountains rise and are eroded, more gold is added beneath them.
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Coarse grained gold in a quartz vein ( the gold is 3 mm across) from the headwaters of the Callery River which flows into the Waiho River at Franz Josef.
Whataroa vein gold. Fine grained gold particle (about 1/100th of a millimetre across, in center of picture) as seen under a microscope. The gold is totally enclosed in pyrite (pale yellow) with grains of arsenopyrite ( white) at the lower right. |
