Arc said the intersections were the second round of pleasing results from Kalaba in less than a month.

Reverse circulation drilling of three 25m holes at the oxide portion of Zamsort's Kalaba area intersected cobalt grades of up to 0.35% and copper grades of up to 1.5%.

Highlights from the drilling were 23m at 1.16% copper equivalent from 2m in one hole, including 10m at 0.81% copper and 0.15% cobalt for 2% Cu-eq from 13m; and 4m at 1.17% copper and 0.22% cobalt for 2.90 Cu-eq from 17m.

At the two other holes, drilling intersected 16m at 1.28% Cu-eq from 9m, including 9m at 0.83% copper and 0.11% cobalt for 1.74% Cu-eq from 13m; and 15m at 1.29% Cu-eq from 10m, including 6m at 0.51% copper and 0.20% cobalt for 2.11% Cu-eq from 14m.

The oxide material will be processed through the commercial scale definition (CSD) plant, which Arc said was on track for commissioning in December.

"Given the prevalence of cobalt in the oxide ore, the plant is also being tested to ensure that the plant is able to maximise cobalt recovery and process a separate cobalt concentrate as well as a separate copper concentrate," the company said.

It was testing two cost efficient systems and had received "encouraging" early results.

Arc executive chairman Nick von Schirnding said the high-grade cobalt mineralisation intersected during the recent round of drilling was encouraging.

"These results from the pit areas immediately adjacent to the CSD plant showed mineralisation that is near-surface and hosted in weathered material that can be mined without the need to drill and blast, which should provide for low strip ratios and correspondingly very low mining costs," he said.

He added work was ongoing to maximise the cobalt recoveries to ensure full value at Kalaba was extracted.

Arc nomad and broker SP Angel said in a note Arc's drilling programme continued to show greater scale and more value in its results.

"The identification of substantially more mineralisation from surface, which can be mined cheaply without blasting will surely add much to the overall project economics," it said.

Despite the pleasing results, Arc's shares slipped 2.51% Wednesday to 3.14p (US4.1c).