Fortune Mojapelo, CEO of Bushveld Minerals PLC LON:BMN, said: “The encouraging metallurgical results achieved support our view that high-grade cassiterite concentrates can be produced from the Groenfontein Deposit with relatively good recoveries. With recently updated plant capex and opex estimates at hand, we look forward to finalising infrastructure and mine cost estimates while continuing to focus attention on accelerating smaller-scale mine development and commissioning. The tin market has been particularly positive in a generally negative commodity environment with the tin price up 18% since the start of the year on supply constraints.”
Bushveld Minerals Limited (AIM: BMN), a diversified mineral development company with a portfolio of vanadium, titanium, iron ore, tin and coal assets in Africa, is pleased has presented DirectorsTalk with results from pilot-scale metallurgical test work and plant design at its Groenfontein Tin Deposit (“Groenfontein Deposit” or the “Deposit”) in Limpopo Province, South Africa.
Highlights
The Groenfontein Deposit test work was intended to assess tin recovery on a plant-scale, gain insight into potential concentrate grades, and to fine-tune plant flow-sheet design parameters. The test work has delivered the following positive results:
-- Expected recovery using gravity concentration of over 70%, for grind sizes of -1 mm;
— Achieved commercial concentrate grade of 74.59% SnO(2) (cassiterite – equivalent to 58.75% Sn);
-- Plant design and flowsheet underway;
— Final costing underway to determine capital and operating expenditure requirements for mining and processing plant establishment, together with ancillary infrastructure; and
— Results to be incorporated into an updated business model focusing on the smaller-scale, near surface high-grade tin targets near-term production.
Bushveld released a scoping study on the Groenfontein and Zaaiplaats deposits in September 2014, which envisaged a mining rate of 691,000 tons per annum at a head grade of 0.12-0.23% SnO(2) to produce 610-1130 tons of refined tin metal per annum post smelting.
Pursuant to the 2014 Scoping Study, the Company decided to revise the development plan for the project to focus on mining the higher-grade zone of the Groenfontein and Zaaiplaats Deposits and processing it using a relatively simple gravity separation flowsheet to produce a saleable concentrate product. The scope revision was driven by the Company’s interest in executing a low capex near term production operation. The aim is to take advantage of a relatively buoyant tin market and establish Greenhills as a stand-alone tin asset.
In order to assess tin recovery parameters on a plant-scale, gain insight into potential concentrate grades, and to fine-tune plant flowsheet design parameters, a large (500 kg) sample of surface ore from historical workings at the Groenfontein Deposit was submitted for additional metallurgical test work at Peacocke & Simpson, minerals processing experts specialising in gravity recovery.
The results show that at a top size of 1 mm, >70% Sn recoveries are achieved for enhanced gravity concentration, less than 15% Sn is lost to tailings during spiralling, and shaking tables achieve at least 85% recovery, giving over 50% cumulative recoveries and a final concentrate grade of 74.59% SnO(2) (58.75% Sn).
Consequently, a flowsheet has been developed for gravity separation, with crushing and screening and rod-milling to -1 mm. Material is concentrated via spirals and shaking tables to maximise recovery and SnO(2) concentrate grade. The plant design envisages a 164,160 tpa operation producing up to 510 tpa SnO(2) .
The next step is to complete flowsheet design and mine-planning studies to determine mine capex and opex parameters, which will be incorporated in a revised financial model.
