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Castle building with high-grade graphite concentrates


Castle Minerals’ Kambale graphite in flotation separation. Credit: File

Castle Minerals says metallurgical testwork on samples from its Kambale graphite project in Ghana shows that production of commercial-standard specification grade for bulk fine-flake graphite concentrate grading 95.1 per cent total graphitic carbon (TGC) is possible using conventional grinding and flotation methods.


The testwork, completed recently at the project that is 100 per cent-owned by the company’s Ghanaian subsidiary Kambale Graphite, was undertaken on 215kg of composited raw, unweathered diamond-drill core from several different graphitic lenses. It provided a representative bulk sample of the anticipated ore-type mineralisation, at an average grade of 11.7 per cent TGC.


An initial series of bench-scale “batch tests” were conducted to assess and characterise the suppled material to assist in the design and optimisation of the testwork circuit and conditions for the planned bulk concentrate production. It was followed by multiple stages of grinding and flotation, which successfully separated the graphite from other mineral phases and removed most of the unwanted gangue materials.


Management says the final rendering of the concentrate resulted in production of a mainly fine-flake graphite with a size of less than 75 microns for a graphite recovery to concentrate of 79 per cent.

This heralds a major advance in our fast-track evaluation of Kambale as a possible supplier of concentrate to be ultimately used in the production of anodes for lithium-ion batteries to power the world’s fast-growing fleet of electric vehicles. An additional 100M to 120M light EVs are forecast to be on the road by 2030. More profound is the extreme reliance of USA and EU vehicle manufacturers on Chinese supplied anodes and batteries. This is being addressed by the construction of numerous battery ‘gigafactories’ but these will need to source their graphite requirements from somewhere other than China. Graphite mines take a lot longer to find and develop than gigafactories. Hence, the Kambale Graphite Project is well positioned as a possible uncommitted supplier of material into the USA and EU markets. Castle Minerals managing director Stephen Stone

The company’s latest outcome is supported by results of its preliminary batch-scale testwork – revealed in September, 2021 – from three composited samples of weathered graphitic schists from surface trenches. Raw graphite grades ran 12.56 per cent, 16.09 per cent and 17.16 per cent total carbon, respectively.


Conventional grind and flotation methods on the samples yielded fine-flake graphite concentrate grades of up to 96.4 per cent and recoveries of 88 per cent, indicating that good consistency exists across the company’s current graphite resource area.


As flagged previously, Castle will send a bulk concentrate from its latest testwork to specialists ProGraphite GmbH in Germany to undergo sizing, shaping, purification and coating. It will then be subject to a series of electrochemical and battery performance tests to determine its suitability for the manufacture of battery anode material (BAM), which is used to make anodes for lithium-ion batteries.


Management says it is winding up its latest 43-hole infill reverse-circulation (RC) drilling program and that the remaining results will be reported shortly. It expects the compilation of the latest drilling results will help qualify additional graphitic zones for inclusion in its planned update of the original mineral resource estimate that stands at 15.6 million tonnes at 9 per cent TGC, containing 1.41 million tonnes of graphite.


Once Castle’s resource upgrade is concluded, it plans to schedule a scoping study during this year’s final quarter to assess the commercial merits of establishing a graphite mining and concentration operation at Kambale. Additionally – and subject to the outcome of testwork in Germany – the study will evaluate the possible on-site production of value-added precursor BAM.


Kambale is Ghana’s only known graphite deposit and is located 6km west of the Upper West capital, Wa. It has reliable grid power, water, good roads and commercial air services. The country is an established and safe mining jurisdiction with a highly-skilled workforce, a strong mining services sector and excellent infrastructure.


At present, there is no viable high-volume substitute for natural flake graphite or synthetically manufactured forms that involve more elaborate and often higher carbon dioxide-generating processes. The immediate medium to long-term outlook for the broader graphite concentrates market is one of escalating demand and a potential supply deficit driven by its global consumption in the fast-growing electric vehicle battery and stationary power storage sectors.


Castle’s Kambale project is rapidly emerging as a strategically-located and well-timed opportunity to service the forecast surge in graphite demand and meet any potential supply deficit in markets involved in global decarbonisation and consequent electrification.


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