Key objectives were set prior to the program and positive outcomes were achieved such as improved gold recoveries in the oxidised saprolite gold ore type and confirmation of appreciable cobalt and gold grades in pyrite concentrates generated from copper tailings.
These outcomes have the potential to substantially enhance project revenues through an expanded open pit and extended mine life.
Havilah technical director Chris Giles said: “Our metallurgical test program is nearing completion and it is apparent that the key objective to improve gold recoveries in the saprolite gold ore was successful.
“We have also confirmed that there is appreciable gold and cobalt in the pyrite concentrates and marketing studies, now underway, will inform us of the terms and likely payability levels we can expect from these metals.
“This new and complete metallurgical information will flow through into trade-off studies and a revised economic model to be incorporated into an updated PFS for Kalkaroo.”
Metallurgy program objectives and outcomes
In an important breakthrough Havilah’s studies show that:
- Excessive copper is unlikely to be an issue when average-grade saprolite gold ore is being treated, provided adequate levels of carbon loading are achieved; and
- As an alternative, an established method involving cold caustic cyanide solution is also effective in reducing copper to manageable levels.
Saprolite ore can therefore be treated by conventional cyanide leaching to achieve measurably improved gold revenues.
Remaining work to complete PFS update
Final metal recoveries from the metallurgical test work and the outcomes of the marketing studies will be used to complete a range of trade-off studies.
The objective of the trade-off studies is to ensure optimal processing and mine scheduling strategies are adopted as the basis for detailed mine optimisation, process engineering and economic modelling.
This phase of work will be supported by RPMGlobal, with the outcomes of the trade-off studies to be incorporated in the updated PFS study due later this year.