oxidized gold ore leching mineral processing operation
Figure 1 depicts
a flowsheet for processing free-milling oxidized gold ore. The kinetics of gold
leaching is slow, and gold ores are frequently ground to less than about 75 μm
before leaching. Even then, one day is usually required in the leaching step.
In this process, run-of-mine ore is crushed and ground. The ball mill discharge in subjected to gravity concentration to
recover the larger particles of free gold. The tailings from this operation are
thickened, and the underflow from the thickeners is then subjected to cyanide
leaching. In some instances, ores may contain oxygen-consuming minerals, such
as pyrrhotite and marcasite, and a preaeration step may be conducted ahead of
cyanide leaching.
Fig1.Flowsheet options for grinding and agitated leaching of free-milling
oxidized gold ores
Heap leaching has
revolutionized the gold mining industry. Low-grade oxidized ores containing approximately
0.03 oz gold per short ton of ore can be processed with this technology,
whereas they could not be processed by the higher cost grinding/agitation
leaching (milling) process. Figure 2 presents a simplified flowsheet of heap
leaching. As the figure shows, run-of-mine ore may or may not be crushed. If crushing is done, the ore is generally
crushed to <2 in. in diameter.
FIGURE 2. Flowsheet for heap leaching
of oxidized gold ores mineral processing
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