South Boulder Mines testing produces commercial-grade potassium sulphate from Colluli

Metallurgical testing has produced commercial-grade potassium sulphate (SOP) and a simple, high-yield SOP processing path at Colluli.

Metallurgical testing has produced commercial-grade potassium sulphate (SOP) and a simple, high-yield SOP processing path at Colluli.

South Boulder Mines (ASX: STB) has revealed that commercial-grade potassium sulphate (SOP) has been produced from a Colluli Project sample, with the metallurgical testing conducted at the Saskatchewan Research Council laboratory in Canada.

This is defining for the company, as production testing affirms a simple, high-yield SOP processing route.

The metallurgical success followed testwork which achieved potassium recoveries exceeding 80% from flotation testing, and eliminated grinding and some thickening infrastructure from initial process design.

Testing will continue to refine the processing route, with a pilot plant to add robustness to the DFS plant design.

South Boulder and the Eritrean National Mining Company (ENAMCO) are equal shareholders of the Colluli Mining Share Company (CMSC) which will develop the Colluli Potash project.

Paul Donaldson, managing director, commented: “The metallurgical testing to date has progressed exceptionally well for our SOP development path. We are excited by the simplicity of the process which is effectively flotation and mixing of recovered potassium salts from the open pit.”

With South Boulder taking the requisite time to get the process design right, this has reduced the process plant capital and demonstrated successful generation of the premium potash product, potassium sulphate.

SOP has historically enjoyed a 35% price premium over potassium chloride though this has grown to over 80%, making it likely that Colluli would produce additional revenue of more than US$290 per tonne.

Colluli is also the closest SOP resource to the coast globally and has the most favourable coastal access from the Danakil depression.

The project is just 75 kilometres to the designated loading point at Anfile Bay and 180 kilometres from the Port of Massawa – a 4 berth bulk and container terminal.

Testing process

Commercial grade SOP has been produced by combining decomposed kainite and sylvite under ambient conditions, affirming the simple, high yield process design developed for feasibility studies

Donaldson added, “We have been thoroughly testing the processing philosophy with our experts in Canada and it is very pleasing to see the optimal path sufficiently matured to produce commercial grade SOP.

“The more we learn about the resource, the more confident and excited we are about the project potential.

“Metallurgical test work will continue to refine this chosen processing path to produce even higher grades and we will be commissioning a pilot plant to use material from Colluli to add robustness to the plant design as we progress from pre-feasibility to definitive feasibility.”

The importance of Colluli SOP

Colluli hosts a globally unique deposit of sylvite, carnallite and kainite salts which will be fully utilized to produce the premium potash product.

Utilisation of all salts reduces mining strip ratio and operating costs, and allows the production of sulphate of potash (SOP) which carries a substantial price premium over potassium chloride (Muriate of potash).

Standard and granular SOP has grades of 50% K20. The Colluli process precipitated above 50% K20 grade SOP as indicated by X-ray Diffraction Analysis (XRD).

Continued refinement of this process path is anticipated to liberate higher grades.

The project has a shallow Resource of 1 billion tonnes of potassium bearing salts, all of which are suitable for the production of potash fertilisers.


Today’s outcome is a very positive one for the company and follows on from a reduction in processing plant capital by conducting additional metallurgical test work and high flotation yields.

The PFS is on track for delivery in early 2015.

As an example of how South Boulder has arrived at this point economically, the company has spent less than $25 million and has proven the process.

Proactive Investors estimates that it should complete all of its studies for less than $40 million.

As a benchmark, potash exploration work that was taking place in Afar State by Yara Dallol BV, a subsidiary of Yara International (STO:YARO), is finalised after a total cost of US$100 million.

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