Copper deposit grades are usually expressed as a weight percentage of the total rock. For example, 1,000 kilograms of copper ore containing 300 kilograms of copper metal has a grade of 30 percent.

The legislation would make permanent a 20-year ban on that type of mining on 225,000 acres of Superior National Forest in the ...

A copper mine in British Columbia produces a metal the world needs to phase out fossil fuels. It holds promise — and danger.

Mining at Gilar commenced earlier this month, with an initial 1 267 t of ore extracted. The ore graded an average of 0.65% copper, with a maximum of 1.63% copper, and 1.36 g/t gold, with a maximum ...