Rafaella Resources Ltd (ASX:RFR) has described the ore sorting test results received from Tomra Sorting Solutions for its flagship Santa Comba tungsten and tin mine in Galicia, northwest Spain, as exceptional.
A grade recovery curve shows potential for more than 90% tungsten recovery, with an increased yield of up to 55% of feed mass.
The overall results showed a 50% rejection of unmineralised rock and near doubling of feed grade, lowering planned process capital and operating expenditures, and enhancing process efficiency through a simpler process flow sheet.
Testing highly positive
Testing of the pre-concentration of Santa Comba ores was highly positive and allows Rafaella to review several opportunities to simplify the process plant thereby reducing capital costs and operating costs for the project.
Tomra's testing of low-grade ores also showed viable recovery from over 2 million tonnes of mineralisation not currently factored into the project’s economics.
Further, the 50% reduction in process tonnage reduces the project’s environmental impact, with a far lower volume of waste generated, lower energy consumption per unit of metal produced and lower water consumption
It is estimated that for a throughput of 1 million tonnes of feed ore and around 500,000 tonnes per year of pre-concentrate, two XRT units would be required.
"Exceeds expectations"
Rafaella managing director Steven Turner said: “The results from the ore sorting test-work have exceeded the company’s expectations.
“The clear discrimination between ore-bearing rock and low-grade or barren rock has delivered high recoveries and yields allowing for a simpler process plant.
“The benefits of this simplification will be significant once the metallurgical studies are completed.
“These results are now being fed into the feasibility study that is in the final stages of completion and the company looks forward to providing the market with these exciting updates on the fast-tracking of its flagship project over the coming weeks.”
Simplified process plant
The highly positive test results allow Rafaella to review several opportunities to simplify the process plant, thereby reducing capital and operating costs.
Tomra's test program tested two bulk samples selected from assayed drill core crushed to two size groups - +8 millimetres to -20 millimetres and +20 millimetres to -40 millimetres.
Sample No 40 was around 1,100 kilograms of average grade ore at 0.15% tungsten trioxide while sample No 41 was around 250 kilograms of low-grade ore at 0.05% tungsten trioxide.
The report’s conclusion was “the results from this test-work were positive for both sizes and samples. Significant upgrades of tungsten trioxide as well as high recoveries were achieved in all test runs for sample '40' using XRT, while leaving rather low grades for tungsten trioxide in the waste fraction.”
The low-grade sample '41' could be upgraded by a factor of 1.7 to 3 and a waste grade between 0.025 and 0.030 is achievable.
Key results
For the process grade tests are as follows:
➢ Maximum recovery was 90% with a product grade of 0.246% tungsten trioxide, a yield of 48% from feed grade of 0.133% tungsten trioxide; and
➢ Maximum head grade was 0.399% tungsten trioxide, recovery of 86.5%, and a 40% yield from feed grade of 0.183.
The 78.17% result was considered a sampling anomaly and diluted by a higher yield but has been left in for completeness.
The low-grade ore treatment results are:
➢ Best recovery was 64.5% with a product grade of 0.1% tungsten trioxide and a 38% yield from a feed grade of 0.058% tungsten trioxide; and
➢ Best head grade was 0.165% tungsten trioxide, 18% yield and 54% recovery from a head grade of 0.055% tungsten trioxide.
