4
Newmont Red Chris Mine
The Red Chris porphyry ore body is located in northern
British Columbia, Canada. This copper-gold deposit has an
average feed grade of 0.35 percent copper (mostly as chal-
copyrite) and 0.35 g/t of gold.
Test work completed at the University of South
Australia and by the vendor13 demonstrated that using a
more electrochemically inert grinding media had a positive
impact on both copper and gold recoveries (by at least 3 and
4 percent, respectively), as well as the potential to reduce
lime consumption. Subsequently, the ball mill was purged
with high chrome grinding media and the pulp chemistry
monitored as the media charge changed from 100 percent
forged steel to 100 percent high chrome.
Converting from forged steel to high chrome saw a 26
percent reduction in media consumption, as well as the
pulp chemistry shift to more oxidising conditions with sig-
nificant increases in the Eh and dissolved oxygen levels in
the pulp and a dramatic decrease in the oxygen demand.
Operating under the new pulp chemistry regime led to an
increase in both the copper and gold recoveries by 0.7 and
2.3 percent, respectively. The lime consumption was also
reduced by 43 percent.
Evolution Northparkes Mines
The Northparkes copper-gold porphyry deposits are
located 27 km north of Parkes in central New South Wales,
Australia. This porphyry copper-gold deposit has an aver-
age head grade of 1.0 percent copper (as bornite and chal-
copyrite) and 0.35 g/t of gold.
The same protocol was followed with samples of ore
tested in the laboratory using the MagoMill ®. In this case
changing from forged steel to high chrome grinding media
saw the Eh increase by nominally 200 mV. The dissolved
oxygen content increased significantly. The oxygen demand
and the EDTA extractable iron both decreased. The labora-
tory copper rougher flotation tests indicated that changing
to Duromax ®T resulted in an increase in copper and gold
recovery of 2.4 and 2.2 percent14.
Northparkes subsequently went to plant trial in
Module 2. Pulp chemistry surveys were completed before
and after converting to high chrome grinding media. These
surveys indicated that the Eh increased by 130 mV, the
dissolved oxygen concentration increased subtly, and both
the oxygen demand and EDTA extractable iron decreased
markedly, indicating that the corrosion rate of the grinding
media had decreased. The statistical analysis of the metal-
lurgical data indicated that the copper and gold recoveries
increased by 1.3 and 1.9 percent, respectively. There was
also a noticeable increase in the copper concentrate grade
of 1.0 percent14.
APPLYING THESE RESULTS TO COPPER-
MOLYBDENUM PORPHYRY ORES
It is apparent from the above discussion that a robust,
well executed laboratory test program completed in the
MagoMill ® is able to not only replicate plant conditions,
but also provide an indication the magnitude of the recov-
ery benefit that can be expected should the plant convert
from forged steel to high chrome grinding media. In terms
of pulp chemistry converting from forged steel grinding
media to a suitable high chrome alloy generally results
in the Eh shifting to more oxidising pulp potentials, the
dissolved oxygen concentration increasing, the oxygen
demand (or reactivity) decreasing and the EDTA extract-
able iron (a measure of the media corrosion) decreasing.
The change in pulp chemistry to more favourable condi-
tions leads to increases in the copper and gold recover-
ies and potential reductions in reagent consumption. For
example, the copper recovery improvement in the labora-
tory for Northparkes was 2.4 percent, and this translated
into an increase of 1.3 percent in the plant. The difference
between the laboratory and the plant improvement is prob-
ably related to variations in the mineralogy between the
two sets of data, and inherent instabilities experienced in
an operating plant. However, it would seem reasonable to
suggest that the laboratory result should be discounted by
around 50 percent for copper recovery.
A Chilean Copper-Molybdenum Porphyry
This copper-molybdenum porphyry deposit has an aver-
age head grade of 0.6 percent copper (as chalcopyrite and
chalcocite) and 100 g/t of molybdenum. The ore contains
nominally 3 percent pyrite.
Laboratory test work was completed using the
MagoMill ® and showed very little difference in the Eh or
dissolved oxygen concentration between for the forged
steel and the high chrome alloys tested. A possible reason
for this was the elevated pH (10.5) employed at this site.
However, it was observed that shifting from forged steel
to high chrome did result in a significant reduction in the
oxygen demand (from 1.71 min–1 to 1.04 min–1), and a
marked decrease in the EDTA extractable iron (from 1.15
percent to 0.62 percent), suggesting that media corrosion
was inhibited when using a more electrochemically inert
grinding media.
These changes in the pulp chemistry resulted in a sig-
nificant improvement in the copper grade/recovery curve
(Figure 2). That is, at 10 percent copper concentrate
Newmont Red Chris Mine
The Red Chris porphyry ore body is located in northern
British Columbia, Canada. This copper-gold deposit has an
average feed grade of 0.35 percent copper (mostly as chal-
copyrite) and 0.35 g/t of gold.
Test work completed at the University of South
Australia and by the vendor13 demonstrated that using a
more electrochemically inert grinding media had a positive
impact on both copper and gold recoveries (by at least 3 and
4 percent, respectively), as well as the potential to reduce
lime consumption. Subsequently, the ball mill was purged
with high chrome grinding media and the pulp chemistry
monitored as the media charge changed from 100 percent
forged steel to 100 percent high chrome.
Converting from forged steel to high chrome saw a 26
percent reduction in media consumption, as well as the
pulp chemistry shift to more oxidising conditions with sig-
nificant increases in the Eh and dissolved oxygen levels in
the pulp and a dramatic decrease in the oxygen demand.
Operating under the new pulp chemistry regime led to an
increase in both the copper and gold recoveries by 0.7 and
2.3 percent, respectively. The lime consumption was also
reduced by 43 percent.
Evolution Northparkes Mines
The Northparkes copper-gold porphyry deposits are
located 27 km north of Parkes in central New South Wales,
Australia. This porphyry copper-gold deposit has an aver-
age head grade of 1.0 percent copper (as bornite and chal-
copyrite) and 0.35 g/t of gold.
The same protocol was followed with samples of ore
tested in the laboratory using the MagoMill ®. In this case
changing from forged steel to high chrome grinding media
saw the Eh increase by nominally 200 mV. The dissolved
oxygen content increased significantly. The oxygen demand
and the EDTA extractable iron both decreased. The labora-
tory copper rougher flotation tests indicated that changing
to Duromax ®T resulted in an increase in copper and gold
recovery of 2.4 and 2.2 percent14.
Northparkes subsequently went to plant trial in
Module 2. Pulp chemistry surveys were completed before
and after converting to high chrome grinding media. These
surveys indicated that the Eh increased by 130 mV, the
dissolved oxygen concentration increased subtly, and both
the oxygen demand and EDTA extractable iron decreased
markedly, indicating that the corrosion rate of the grinding
media had decreased. The statistical analysis of the metal-
lurgical data indicated that the copper and gold recoveries
increased by 1.3 and 1.9 percent, respectively. There was
also a noticeable increase in the copper concentrate grade
of 1.0 percent14.
APPLYING THESE RESULTS TO COPPER-
MOLYBDENUM PORPHYRY ORES
It is apparent from the above discussion that a robust,
well executed laboratory test program completed in the
MagoMill ® is able to not only replicate plant conditions,
but also provide an indication the magnitude of the recov-
ery benefit that can be expected should the plant convert
from forged steel to high chrome grinding media. In terms
of pulp chemistry converting from forged steel grinding
media to a suitable high chrome alloy generally results
in the Eh shifting to more oxidising pulp potentials, the
dissolved oxygen concentration increasing, the oxygen
demand (or reactivity) decreasing and the EDTA extract-
able iron (a measure of the media corrosion) decreasing.
The change in pulp chemistry to more favourable condi-
tions leads to increases in the copper and gold recover-
ies and potential reductions in reagent consumption. For
example, the copper recovery improvement in the labora-
tory for Northparkes was 2.4 percent, and this translated
into an increase of 1.3 percent in the plant. The difference
between the laboratory and the plant improvement is prob-
ably related to variations in the mineralogy between the
two sets of data, and inherent instabilities experienced in
an operating plant. However, it would seem reasonable to
suggest that the laboratory result should be discounted by
around 50 percent for copper recovery.
A Chilean Copper-Molybdenum Porphyry
This copper-molybdenum porphyry deposit has an aver-
age head grade of 0.6 percent copper (as chalcopyrite and
chalcocite) and 100 g/t of molybdenum. The ore contains
nominally 3 percent pyrite.
Laboratory test work was completed using the
MagoMill ® and showed very little difference in the Eh or
dissolved oxygen concentration between for the forged
steel and the high chrome alloys tested. A possible reason
for this was the elevated pH (10.5) employed at this site.
However, it was observed that shifting from forged steel
to high chrome did result in a significant reduction in the
oxygen demand (from 1.71 min–1 to 1.04 min–1), and a
marked decrease in the EDTA extractable iron (from 1.15
percent to 0.62 percent), suggesting that media corrosion
was inhibited when using a more electrochemically inert
grinding media.
These changes in the pulp chemistry resulted in a sig-
nificant improvement in the copper grade/recovery curve
(Figure 2). That is, at 10 percent copper concentrate