Cyanide vats

Cyanide vats

The development of the cyanide process for extracting gold and silver from crushed quartz revolutionised hard-rock gold mining in New Zealand in the 1890s. Before cyanide, a mercury amalgam was used to chemically recover gold and silver, but it was only half as effective. Cyanide allowed far more of the gold and silver to be recovered, making previously marginal mining operations profitable. These large vats hold cyanide and crushed ore.