QMines confirms high copper-gold recoveries from Mt Chalmers core samples
QMines says further testing is needed to determine the optimal process to achieve high recoveries from Mt Chalmers.
New metallurgical work on core samples from the Mt Chalmers project in Queensland has confirmed high copper and gold recoveries for owner QMines (ASX: QML).
Testing by Perth-based Como Engineers was designed to maximise gold recovery while achieving a grind and reagent regime suitable to produce a clean copper concentrate containing gold and silver.
It also aimed to upgrade the project’s copper float tail to one or more saleable concentrates containing zinc, lead, gold and silver.
Stringer zone testwork achieved 23% copper in concentrate at 98% copper recovery, with significant gold credits of 8 grams per tonne gold.
Differential flotation of massive sulphide copper-zinc concentrates delivered 18% copper and 4.7% zinc, with a separate zinc concentrate grade of 50% zinc and 0.59% copper.
The results build on testwork conducted in 2022, which established a preliminary flowsheet and determined working recovery grades for stringer and massive sulphide concentrates from Mt Chalmers.
QMines said metallurgical tests are ongoing – incorporating work on intermediate grinds, optimised reagents and blends — to progress a feasibility study on the deposit and deliver a maiden ore reserve statement.
Stringer testwork
Previous testwork of the Mt Chalmers stringer mineralisation using a half core composite sample produced a 12.3% copper concentrate with 97% recovery.
The latest testwork on grind size and laboratory flotation methods produced considerably higher grades including 23% copper in concentrate with 98% recovery.
Each of the tests produced a potentially marketable copper product with significant gold credits.
The lead-zinc-silver grade in the stringer composite was low and excluded from the flowsheet to simplify the circuit.
Massive sulphide testwork
Previous testwork on the massive sulphide mineralisation (copper, lead and zinc exhalite) from the same half core sample produced rougher concentrates and determined that further float optimisation was required to create separate and improved concentrate streams for each metal.
To this end, further testing of the sample with a head grade of 1.35% copper, 1.51% lead, 3.64% zinc, 10.6g/t gold and 18g/t silver was subjected to 12 open circuit flotation tests.
Four bulk flotation tests were followed by eight rougher-cleaner circuit tests for copper and zinc concentrates.
Bulk flotation produced a medium grade sulphide concentrate assaying up to 7.54% copper at a recovery of between 53.6% and 98.2% copper.
Upgrade challenges
QMines said while all the minerals were activated, it was challenging to upgrade the bulk concentrate into separate clean concentrates as the process would require depression of already-activated zinc minerals.
As a result, selective flotation tests were conducted with much greater success.
The cleaner copper test was able to produce a result ranging between 13% to 22.3% copper in concentrate at copper recoveries of between 28% and 94.1%.
Separately, a zinc concentrate of between 27.1% and 56.3% was achieved at zinc recoveries of between 30.8% and 59.9%.
QMines confirmed further testing is needed to determine the optimum process to achieve high recoveries closer to the targeted 20% copper and 50% zinc in concentrates.
A separate lead circuit will also be studied.