Oxide Ore

Mineralized rock that has been subjected to weathering and oxidation of primary minerals. Oxidation tends to make an ore more porous. This permits a more complete permeation of cyanide solutions so that the minerals can be readily dissolved.

Oxide ores are a particular feature of the open-pit mining in Australia and the United States, which expanded so rapidly in the 1980s. These ores, especially those in Nevada, could be treated by heap leaching. The contrast is with the sulphide ores underlying them, which can usually be reached only by much more costly underground mining and which require more complex mineral processing technology to release the gold.