AN ongoing metallurgical test programme and plant design test at multicommodity explorer Premier African Minerals’ RHA tungsten project in Kamativi area in Matabeleland North province has produced “encouraging” results, the group’s latest report indicates.World tungsten demand is growing at an annual rate of approximately five percent and the investment is set to boost mining in Zimbabwe.

The programme consisted of investigative work on a 200kg bulk sample, as well as a mini pilot run on a 800kg of bulk sample, both originating from seven separate locations within the historic underground workings.

Based on the mini pilot run, which consisted of crushing, scrubbing and screening the sample to a -6 mm +1 mm and a -1 mm fraction, the test flow sheet produced concentrates of -6 mm +1 mm at 62.7 percent of tungsten oxide and -1 mm at 67 percent tungsten oxide at a cumulative recovery of 77.3 percent.

The process flow had not yet been optimised and the simple flow sheet provided the flexibility to potentially increase the -6 mm +1 mm fraction concentrate grade through a shallower jig cut.

In practice, Premier said it was likely that it would achieve a higher grade at this same recovery, as the full-scale process plant operation was continuous and the cuts on the spirals and tables easier to maintain.

“Determination of the concentrate grade and process recovery is a significant milestone in the development of the RHA mine. The fact that these positive results were achieved on a mini pilot scale allows us to finalise the flow sheet and plant design and proceed to order,” commented CEO George Roach last week.

Tungsten is a strategic metal that is essential in such applications as steel tools and cutting blades, defence applications, alloys, lighting and electronics.

In addition, investigative work on the 200kg sample confirmed the ability to efficiently preconcentrate the plant feed at -25 mm +6 mm by achieving a fourfold upgrade of feed grade at a 20 percent mass pull.

“These results provide the ability and flexibility for the plant to accommodate significantly higher run-of-mine feed rates with the simple addition of jigging capacity upfront,” said the company.

The two grades of concentrate produced from a simple and low-cost process may, in principle, be optimised to customer specifications in terms of material sizing by staged crushing, screening and gravity concentration.

Roach said the group was advancing discussions on offtake and marketing agreements, adding that Premier would now update the economic model contained in its conceptual mining study released in September last year, based on the most recent results and the enhanced resource announced in May.

World supply declined from 90,800 metric tonnes in 2006 to 72,000 tonnes in 2013.

China produces approximately 85 percent of world tungsten supply but has greatly restricted tungsten exports to keep pace with its own industrial demand.

The vertically integrated nature of Chinese production combined with the Chinese government quotas for minor metals have restricted exports of both concentrates and APT from China.

Tungsten is one of few metals to have withstood the recent metals bear market with its prices having shot up from $50 per MTU in 2002 to $400 in H2 2013.

Zimbabwe’s mining sector has shown a significant recovery over the last five years, with an overall upward trend in mineral production.

Mining contributes significantly to the economy in export earnings. Zimbabwe’s natural resource riches offer strong upside opportunities across many commodities. – Miningweekly.com/Business Reporter.

 

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