This scheme was soon replaced by chlorate-sulphuric acid-soda leaching with gravity concentration
at the process head.
The earliest method, other than collecting it by hand, was by gravity concentration
in water but modern mining utilises up-to-date technology.
In the first 15 weeks of operation, the mine produced 193,000 oz of gold, more than half of it as free gold recovered by simple gravity concentration
. Mining operations are scheduled to reach peak output of 30 Mt/y in 2002.
This upgrade includes realigning the Steinert Ore-Sorter output to feed directly to the processing circuit, installing a regrind circuit, and adding flotation capacity to the current gravity concentration
Today various physical cleaning techniques like gravity concentration
, flotation, electric and magnetic separation and oil agglomeration, are in use for the beneficiation of coal (Chen, 1998).
The outcome from the programme suggests the resource could be economically treated using standard Gravity Concentration
/ Carbon in leach (CIL) cyanidation technology.
In South Africa, the company has added to stockpiles, bringing the total stocks of materials for processing to 44,050 oz, equating to four years of current woodchip production capability, three years of gravity concentration
capacity and three years of leach capacity.
Roughly 80 percent of the gold from Rock Creek can be recovered using a simple grind and gravity concentration
process, he said.
Moreover, unlike most gravity concentration
systems which prefer closely sized material, the RAC works well on a broad size range of material.
Testing has included evaluation of cyanide heap leaching, grind - agitated leaching, gravity concentration
, flotation, and flotation concentrate regrind with agitated leaching.