JOHANNESBURG (miningweekly.com) – Havilah Resources is focusing on becoming a substantial cobalt and copper producer, following the discovery of appreciable quantities of cobaltian pyrite, an iron sulphide mineral that has a high cobalt content, at the undeveloped copper sulphide deposits in its portfolio, including the Kalkaroo, North Portia and Mutooroo deposits.
The company, which currently has a Joint Ore Reserves Committee- (JORC-) compliant mineral resource inventory of 915 000 t of copper and 2.33-million ounces of gold in north-eastern South Australia, on Monday said it was aiming to implement a medium-term strategy that will see its cobalt resources developed in conjunction with its copper resources.
Mutooroo has an estimated measured and indicated sulphide resource of 5.9-million tonnes of 1.31% copper and 0.14% cobalt, within a total sulphide resource estimate of 12.5-million tonnes of 1.53% copper. “There is scope to materially increase the resource base as only a portion of the known 2.1 km strike has been drilled to JORC resource status,” the company said in a statement.
Kalkaroo is also a potentially large cobalt resource, with substantial zones containing more than 500 parts per million cobalt that is also hosted in cobaltian pyrite. It is estimated that the Kalkaroo deposit contains five-million to ten-million tonnes of cobaltian pyrite that ranges from 1% to 3% contained cobalt.
“This translates into a substantial cobalt inventory and could significantly boost Kalkaroo mining revenues. At both Kalkaroo and Mutooroo, it is anticipated that the pyrite will be recovered as a clean concentrate in a final stage of the copper flotation process,” Havilah said.
There are two main options to recover cobalt from the cobaltian pyrite - leaching and roasting. “The roasting alternative produces the best revenue stream, but is capital intensive and requires a long-term market for the sulphuric acid that is produced.
“Leaching is potentially less capital intensive and will produce saleable cobalt salts. Our basic leaching experiments to date show that an extremely acid solution is moderately effective in leaching the pyrite and releasing cobalt,” the miner pointed out.
Initially, it is expected that cobalt in the cobaltian pyrite concentrate will be recovered through a leaching process, with Havilah seeking investment funds in the longer-term to build a roaster and acid plant, contingent in large part on securing markets for the sulphuric acid that will also be produced.