GOLD
EXTRACTION
GOLD
EXTRACTION
electrowinning or precipitation. Following this,
the precipitate, carbon or electrodes are refined to
recover “999 gold”, plus other strategic metals.
The company claims it owns the “only cost-
effective alternative to cyanide”, which has a
broad applicability in most ores, offers fast leach
kinetics, and is environmentally friendly and
sustainable.
In recent studies carried out by the company
and SGS on two separate samples of high-grade
ore that compared the EnviroLeach process with
cyanide, EnviroLeach outperformed cyanide on
As part of the thiosulphate process at
Goldstrike, gold-bearing, sulphur-based ore is
heated as a thick slurry of ore, air, water and
limestone in large pressure chambers or
autoclaves and then pumped into the ‘resin-in-
leach’ circuit that takes place inside large
stainless steel tanks, according to CSIRO
mine life, according to CSIRO.
“This new technology literally delivers a new
gold standard for the global gold industry,”
CSIRO said.
Clean Mining is currently in negotiations with
ICA Mining Services, in the Northern Territory of
Australia, to commission the first commercial
plant to process gold using this technology, and
with Nu-Fortune Gold to commission a plant, in
both overall recoveries and leach kinetics,
according to the company.
Twenty-four-hour leach tests were performed as
part of a continued strategic collaboration between
the company and several gold producers. The tests
the Goldfields of Western Australia.
EnviroLeach Technologies believes its own
patent-pending process can provide a more
environmentally friendly and safe alternative to
the 66,000 t/y of cyanide used in the mining
industry and has recently carried out testing to
prove how it can compete with the lixiviant from
a recovery perspective.
The company’s patent-pending process sees
material prepared using separation, grinding and
classification before the ground material is
dissolved in the lixiviant for a pre-specified time.
The metals are then recovered from the solution
using ion exchange, carbon absorption,
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were conducted on high-grade ore and flotation
concentrates using the EnviroLeach formula
compared with a high-grade 5 g/l cyanide solution.
SGS was contracted to conduct the cyanide leach
tests for the comparison.
The tests on the high-grade ore sample, with
an assayed gold head grade of 675 g/t, showed
the most favourable results with the EnviroLeach
formula attaining gold recoveries of over 99% in
under six hours, with cyanide attaining
recoveries of 94% in 24 hours.
Testing of flotation concentrate with an
assayed gold head grade of 55.1 g/t showed high
gold recoveries of over 90% by EnviroLeach in six
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The SAG Conference event brings together all those engaged
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50 International Mining | AUGUST 2019
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