New test results have boosted Red Metal’s confidence in exploiting its Sybella rare earth oxide (REO) discovery through a low-cost heap-leach processing operation.

The company is seeking the most economically effective way to process ores from the Mount Isa project, which have unique metallurgical properties.

It said the latest leach and comminution results confirmed strong REO extractions could be achieved using low levels of ambient temperature sulphuric acid on coarse fractions of both weathered and fresh granite from the site.

Test work shows coarser heap leach crush sizes (-10mm to -15mm) can provide high REO recoveries with less contaminant liberation and less acid consumption, meaning high revenue and lower processing costs.

The company said a breakthrough pH 3 leach result achieved on -15mm fresh granite run over 56 days had opened up vast tonnage potential below the weathered zone at Sybella to possible REO extraction.

“Interim results from the second phase of leach test work and comminution studies have confirmed Red Metal’s initial hypothesis that the Sybella granite-hosted REO mineralisation can be coarsely crushed and leached under weak acid conditions in a manner suitable for low-cost, low-capital heap leach processing,” managing director Rob Rutherford said.

“Impurity removal trials are progressing with early indications showing residual contaminants from the pregnant leach solution may be successfully removed, potentially resulting in a premium mix rare earth carbonate (MREC) product.

“Results from these tests are expected shortly. The company has reasonable expectation that our ongoing studies will confirm a process route that optimises REO recovery (increases revenue) but reduces the acid consumption rate and ensures that impurities in the final product can be satisfactorily minimised (lowering processing costs).

“It is also now working rapidly towards outlining ore resources.”

A broad-spaced step-out drilling program is being carried out at Sybella, 20km south-west of Mount Isa (image at top of page).

Preparations are underway for follow-on column leach test work using very weak acids (pH 2 to pH 3.5) over extended residence times (more than 120 days) with the aim of further improving REO recoveries, reducing acid consumption and lowering contaminants in the resulting pregnant leach solutions.