Typical Open Cut Grades
Gold is generally extracted in open-pit mines at 1 to 2 ppm (grams per tonne) but in certain cases, 0.75ppm gold is economical. This was achieved by bulk heap leaching at Alkane Minerals Ltd. Peak Hill mine in western New South Wales, near Dubbo, Australia.
Nickel, generally as laterite, is extracted via open-pit down to 0.2%. Copper is extracted at grades as low as 0.15% to 0.2%, generally in massive open-pit mines in Chile, where the size of the resources and favorable metallurgy allows economies of scale.
Materials typically extracted from open-pit mines include:
- Clay
- Coal
- Copper
- Coquina
- Diamonds
- Gravel and stone (stone refers to bedrock, while gravel is unconsolidated material, as found in glacial or fluvial deposits)
- Granite
- Gritstone
- Gypsum
- Limestone
- Marble
- Metal ores, such as Copper, Iron, Gold, Silver and Molybdenum
- Uranium
Read more about this topic: Open-pit Mining
Famous quotes containing the words typical, open, cut and/or grades:
“It is indeed typical that you Earth people refuse to believe in the superiority of any world but your own. Children looking into a magnifying glass, imagining the image you see is the image of your true size.”
—Franklin Coen. Joseph Newman. The Monitor (Douglas Spencer)
“The role of the writer is not simply to arrange Being according to his own lights; he must also serve as a medium to Being and remain open to its often unfathomable dictates. This is the only way the work can transcend its creator and radiate its meaning further than the author himself can see or perceive.”
—Václav Havel (b. 1936)
“If pregnancy were a book they would cut the last two chapters.”
—Nora Ephron (20th century)
“Kindliness seems to exist primarily as an animal instinct, so deeply rooted that mental degeneracy, which works from the top down, does not destroy it until the mind sinks to the lower grades of idiocy.”
—Charles Horton Cooley (1864–1929)