Great Boulder Resources Limited (ASX: GBR) is a mineral exploration and mining company which has its primary operations in Eastern Goldfields Region of Western Australia. It focuses on the discovery, exploration and delineation of nickel-copper-cobalt and gold resources in WA region wherein the company has a concentrated portfolio of five exploration projects.
On 5th March 2019, the company announced that it has been able to achieve strong results from initial metallurgical testwork which was completed on samples of composite diamond drill hole from the Mt Venn deposit, within the Company’s Yamarna project in Western Australia.
Mt Venn contains Copper mainly as chalcopyrite, and nickel and cobalt in solid solution in pyrrhotite on which the metallurgical testwork was completed. The test was conducted to demonstrate viable flowsheet that would maximize recovery for multiple, high-value products containing copper, nickel and cobalt.
To produce the Copper concentrate, Copper is recovered through a conventional flotation circuit. On the other hand, to produce high purity nickel-cobalt sulphide concentrate, nickel and cobalt are recovered from a separate bulk concentrate through a hydrometallurgical circuit.
The leaching circuit captured the majority of copper rejected from the floatation circuit, and also recovered over 90% of nickel and cobalt from pyrrhotite which has produced a high purity (46% Cu) sulphide. The overall copper recovery improved to above 90% when this high-quality sulphide was combined with the flotation concentrate.
The company is expecting an improvement in recoveries through the flotation and leach circuits from the recent drilling at the Eastern Mafic and Winchester, which has identified significantly higher grade and tenor nickel sulphide. This is higher than the low-grade sample, containing 0.43% Cu, 0.18% Ni and 0.06% Co on which the metallurgical testwork was completed.
Metallurgical Testwork Summary
A clean copper flotation concentrate was produced in the flotation circuit grading between 16 and 20% Cu with no deleterious elements. High purity copper sulphide (46% Cu) produced from the hydrometallurgical circuit is mixed with this flotation concentrate to generate a combined saleable +20% Cu concentrate at over 90% overall recovery.
Nickel and cobalt, to the extent of 90% were recovered into a bulk concentrate following copper flotation. The nickel and cobalt upgrade into the bulk concentrate is modest (~70%) to 0.31% Ni and 0.10% Co, which reflects the tenor of metal in sulphide.
Considerably higher nickel tenor of 1-3% Ni has been returned from the drilling at the Eastern Mafic and Winchester projects which is expected to positively influence the future nickel and cobalt upgrade to the hydrometallurgy circuit and recoveries.
Two leaching processes were investigated to produce high-value sulphide products that are in demand in the battery and EV markets namely: Atmospheric oxidative leach test, which indicated good metal recoveries of over 85% and Pressure oxidation test (POX), which improved quality of leach solution for downstream processing.
Earlier on 18th February 2019, Great Boulders announced its drilling commencement at the Easterm Mafic complex.
As on 5th February 2019 (AEST: 02:31 PM), the stock price is trading at A$0.180. In the year 2019, the stock has given the YTD return of 28.57% whereas the past 1-year return stands at -30.7%, as on 4 March 2019.
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