Gold mining is estimated to create 40,000 pounds (18,000 kg) of waste to yield enough gold for one 18-karat gold ring. When gold is mined from the ground, it typically is mixed with other rock that needs to be separated in order to process the gold. This excess rock is known as waste rock. Waste rock generally has no other use and is disposed of. Some mines treat waste rock with toxic substances, such as cyanide, to help separate it from the gold. Many countries have specific laws about how waste rock must be handled, to prevent contaminating water supplies, for example.
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