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:
“Sinclair Lewis is the perfect example of the false sense of time of the newspaper world.... [ellipsis in source] He was always dominated by an artificial time when he wrote Main Street.... He did not create actual human beings at any time. That is what makes it newspaper. Sinclair Lewis is the typical newspaperman and everything he says is newspaper. The difference between a thinker and a newspaperman is that a thinker enters right into things, a newspaperman is superficial.”
—Gertrude Stein (1874–1946)
“The attempt to be an ideal parent, that is, to behave correctly toward the child, to raise her correctly, not to give to little or too much, is in essence an attempt to be the ideal child—well behaved and dutiful—of one’s own parents. But as a result of these efforts the needs of the child go unnoticed. I cannot listen to my child with empathy if I am inwardly preoccupied with being a good mother; I cannot be open to what she is telling me.”
—Alice Miller (20th century)
“The power of a text is different when it is read from when it is copied out.... Only the copied text thus commands the soul of him who is occupied with it, whereas the mere reader never discovers the new aspects of his inner self that are opened by the text, that road cut through the interior jungle forever closing behind it: because the reader follows the movement of his mind in the free flight of day-dreaming, whereas the copier submits it to command.”
—Walter Benjamin (1892–1940)
“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)