1592 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
given ore block are sufficient to assign it to an ore type and
predict the metallurgical response based on test results.
Based on the results above, including both the OoM
predictions of flotation response from blended ore types
and the confirmation from variability testing, an approach
of blending the underground and open-pit ores, at a mini-
mum ratio of 10 open pit volumes to 1 underground
volume, directly at the Kennecott primary crusher was
adopted for inclusion in the Feasibility Study (Figure 5).
No changes to the current Copperton Concentrator were
required under this strategy and it was predicted that the
designed nameplate of 180,000 tpd would be unchanged
on introduction of underground ore.
Feasibility (FS) Geo-metallurgical Approach
The FS study (completed in 2022) continued to build
on prior findings, and testing was conducted on the core
from additional new drilling. Variability testing was again
included, and the three ore types from PFS were kept as
final ore type categories. Composite samples were then pro-
duced for each of the high and low sulfur ore types. These
composite samples were used for cleaner flotation testing to
fine tune concentrate grade predictions.
Importantly, considerable open-pit co-mingled ore
testing was conducted during the FS. Surface ore composite
samples were blended with the underground ore type com-
posites, and flotation testing was conducted on the blends.
The goal of these blended tests was to look for observable
poisoning or synergy effects in the blends that may have
been missed during OoM work. Some surface skarn ore
types are known to interfere with the flotation response of
other surface ores. This poisoning effect requires stockpiling
Figure 4. Linear relationship between sulfur concentration and pyrite concentration
of certain surface skarn ore types so that it can be processed
alone. There was concern that underground skarn ores
could have a similar effect.
The results of the blending program showed that there
was not a risk of poisoning but on the contrary, there was
an observable synergistic effect from blending the under-
ground and open pit ores. This synergistic effect was seen
with both low sulfur and high sulfur ore types. A blended
feed of 1:10 underground to surface ore resulted in higher
overall copper recovery than the mathematical weighted
average of the individual ore types predicted. In addition,
the concentrate grades were significantly higher than for
either of the ore types by themselves. This effect was par-
ticularly beneficial for the high sulfur ore type, due to a low
predicted concentrate grade of only 9.1% when processed
by itself.
The calculated synergistic effect of blending under-
ground and open-pit ores was attributed to limited froth
carrying capacity, as discussed earlier. Due to the very high
sulfur content of the feed in stand-alone underground tests,
there was limited capacity for the froth to remove sulfides
from the flotation cells within the parameters of the test.
As such, copper recovery was decreased and pyrite com-
petition from high sulfur ore led to decreased concentrate
grades. With the release of the froth capacity constraint,
due to dilution of sulfides by open-pit ore, the blend recov-
ery and concentrate grades increased to be higher than the
calculated weighted average from the individual ore types.
Results from the blend tests allowed for more accurate
modelling of the concentrator response to blended feed to
predict metal recoveries and concentrate quality for feed to
the smelter. The results also highlight the importance of
given ore block are sufficient to assign it to an ore type and
predict the metallurgical response based on test results.
Based on the results above, including both the OoM
predictions of flotation response from blended ore types
and the confirmation from variability testing, an approach
of blending the underground and open-pit ores, at a mini-
mum ratio of 10 open pit volumes to 1 underground
volume, directly at the Kennecott primary crusher was
adopted for inclusion in the Feasibility Study (Figure 5).
No changes to the current Copperton Concentrator were
required under this strategy and it was predicted that the
designed nameplate of 180,000 tpd would be unchanged
on introduction of underground ore.
Feasibility (FS) Geo-metallurgical Approach
The FS study (completed in 2022) continued to build
on prior findings, and testing was conducted on the core
from additional new drilling. Variability testing was again
included, and the three ore types from PFS were kept as
final ore type categories. Composite samples were then pro-
duced for each of the high and low sulfur ore types. These
composite samples were used for cleaner flotation testing to
fine tune concentrate grade predictions.
Importantly, considerable open-pit co-mingled ore
testing was conducted during the FS. Surface ore composite
samples were blended with the underground ore type com-
posites, and flotation testing was conducted on the blends.
The goal of these blended tests was to look for observable
poisoning or synergy effects in the blends that may have
been missed during OoM work. Some surface skarn ore
types are known to interfere with the flotation response of
other surface ores. This poisoning effect requires stockpiling
Figure 4. Linear relationship between sulfur concentration and pyrite concentration
of certain surface skarn ore types so that it can be processed
alone. There was concern that underground skarn ores
could have a similar effect.
The results of the blending program showed that there
was not a risk of poisoning but on the contrary, there was
an observable synergistic effect from blending the under-
ground and open pit ores. This synergistic effect was seen
with both low sulfur and high sulfur ore types. A blended
feed of 1:10 underground to surface ore resulted in higher
overall copper recovery than the mathematical weighted
average of the individual ore types predicted. In addition,
the concentrate grades were significantly higher than for
either of the ore types by themselves. This effect was par-
ticularly beneficial for the high sulfur ore type, due to a low
predicted concentrate grade of only 9.1% when processed
by itself.
The calculated synergistic effect of blending under-
ground and open-pit ores was attributed to limited froth
carrying capacity, as discussed earlier. Due to the very high
sulfur content of the feed in stand-alone underground tests,
there was limited capacity for the froth to remove sulfides
from the flotation cells within the parameters of the test.
As such, copper recovery was decreased and pyrite com-
petition from high sulfur ore led to decreased concentrate
grades. With the release of the froth capacity constraint,
due to dilution of sulfides by open-pit ore, the blend recov-
ery and concentrate grades increased to be higher than the
calculated weighted average from the individual ore types.
Results from the blend tests allowed for more accurate
modelling of the concentrator response to blended feed to
predict metal recoveries and concentrate quality for feed to
the smelter. The results also highlight the importance of