Mining and mineral processing company Cobalt Blue (ASX:COB) reports it has produced ‘high-grade’ concentration results from its Demonstration Plant at the Broken Hill Cobalt Project in New South Wales.
The company says the Concentrator Circuit has now completed operations supporting the Definitive Feasibility Study (DFS), and a total of 4,200 tonnes of ore have been processed to produce 680 tonnes of wet concentrate.
A further 800 to 1,000 tonnes of ore remains for optimisation studies in the future. Cobalt Blue also reports operations were held over 65 days with the longest run of over 100 hours recorded.
Mass recovery of around 17% to 20% was consistently achieved with average grade concentrate grades of 4,434ppm cobalt (Co), and survey samples were obtained from the Concentrator Circuit and independently assayed by a third-party accredited laboratory.
The company says a ‘wide variety’ of ore grade was processed which confirmed regardless of ore grade, a consistent grade of concentrate was produced. Daily average ore grades varied from 600ppm to 1,300ppm, with the concentrate consistently between 4,000ppm to 5,000ppm.
Cobalt Blue Chief Executive Officer (CEO) Joe Kaderavek says: “This is large-scale and technically substantial proof of our concentration operation. Converting over 4,000 tonnes of variable low to high-grade ore to a consistent high-grade concentrate is a major project enabling step.
“This is large-scale and technically substantial proof of our concentration operation”
Put another way, our refinery is 20% of the size of the mine and will see an average of around 4,400ppm concentrate for the life of operations. Concentrate recoveries of up to 9% well exceed our Prefeasibility Study (PFS) baseline.”
Cobalt Blue reports ore processed via the Concentrator Circuit was extracted from the Pyrite Hill Deposit by means of underground development. The company states this deposit extends over 1.2km along strike, over 300m down-dip and varies in thickness from 10m to 100m.
Mineralisation at Pyrite Hill is hosted by a quartz-albite gneiss and is characterised by the presence of disseminated pyrite concentrated parallel to primary foliation.
Ore drive development extracted material between 257mRL and 262mRL around 40m to 50m below surface and 3m to 6m below the interpreted top of fresh rock.
Cobalt Blue says the treatment of cobalt-pyrite involves 2 key steps. The first is conversion of pyrite into pyrrhotite and elemental sulphur followed by leaching of the pyrrhotite. The solubilised cobalt is then recovered by precipitation as a mixed hydroxide with grades of 30% cobalt and 7% nickel.
Following initial commissioning in September this year, kiln operating parameters continue to be optimised to maximise pyrite to pyrrhotite conversion. The company reports the kiln is now in continuous operation with feed rates between 150kg per hour to 200kg per hour.
The kiln will initially focus on production of calcine for leaching, with clean sulphur recovered once a specialised heat-exchange condenser is operational and sulphur prilling equipment installed in Q1 2023.
It also reports the leaching autoclave has been commissioned with the first 2 tonnes of kiln product. Ahead of leaching, the kiln calcine was upgraded to 75% to 85% pyrrhotite and 0.6% cobalt, with residual gangue to be recycled to the float cell to recover unreacted pyrite. This upgrade step reduces the load of inert material progressing into the leach.
Cobalt Blue reports the first MHP is expected later this month, with continuous operation of the leach and MHP circuits planned from January 2023.
The Demonstration Plant operations are on track to deliver the initial process plant design criteria for the DFS, and the company states the Plant will continue to run through the first half of 2023 to obtain large samples of cobalt and sulphur products for market acceptance, and to obtain reliability data for the DFS.
Cobalt Blue is a mining and mineral processing company focused on the development of the Broken Hill Cobalt Project in New South Wales. The portfolio of 3 granted tenements in a total area of 49km-square containing ‘large-tonnage’ cobalt-bearing pyrite deposits are located 23km west of Broken Hill.
Images: Cobalt Blue Holdings Ltd
