Sherwood Copper’s Minto Mine processes a high grade copper–gold deposit in Yukon, Canada. The ore
mined is from a primary copper sulphide deposit with separate additional deposits of copper oxides.
In conjunction with Ausmelt Chemicals, Minto is currently investigating options to recover copper oxide
and sulphide minerals using flotation by blending their primary sulphide ore with oxide ores. The blend
used in this laboratory scale investigation was 70% sulphide ore and 30% oxide ore on a weight basis. The
copper sulphides present in the blend were bornite and chalcopyrite, while the oxides were malachite
and minor azurite.
From previous flotation investigations of mixed copper oxide and sulphide minerals using xanthate and
hydroxamate collectors it was hard to distinguish the impact of the alkyl hydroxamate collector on sulphide
recovery as the sulphide and oxide minerals occurred naturally together. In the case of the Minto
operation the copper oxide and sulphide minerals occur in separate ore deposits and can be treated separately
or blended together. This investigation has shown that using n-octyl hydroxamates (AM28 made
by Ausmelt Limited) in conjunction with traditional sulphide collectors can successfully simultaneously
recover copper sulphides and oxides by flotation from blended ore minerals. The copper sulphide recovery
did not decrease when processing the blended ore compared to treating the sulphide ore independently.
At a blend of 70% sulphide ore and 30% oxide ore, the rougher scavenger copper recovery was
as high as 95.5%. The copper recovery from the blended ore using a mixture of collectors was shown
to be superior to the recovery obtained using only xanthate after controlled potential sulphidisation