THE DRILL SERGEANT: Global Geoscience (ASX: GSC) announced the results of the latest acid-leach testwork carried out at the company’s 100 per cent-owned Rhyolite Ridge lithium-boron project in Nevada, USA.
Global Geoscience said the latest vat leach testwork demonstrated that over 90 per cent of the lithium and boron was extracted into solution in less than seven days.
The company said the decrease in leach time, acid consumption and solution requirements are expected to result in lower capital and operating costs than previously envisaged.
Latest results from the recent optimisation showed:
Much faster leach times of less than seven days – a reduction of more than 50 per cent;
Lower acid consumption of less than 400 kilograms of acid per tonne of feed – a reduction of more than 15 per cent;
Higher lithium and boron concentration in Pregnant Leach Solution (PLS), reducing mechanical evaporation requirements;
Faster, more selective leaching means lower levels of other elements in the PLS;
Continued high recoveries to PLS – greater than 90 per cent for both lithium and boron;
Preparation for vat leaching requires only a coarse crush of 25 millimetres; and
No grinding, agglomeration, high temperature or high pressure required.
“The latest vat leach results represent a significant improvement on already favourable acid-leach results and clearly demonstrate the advantages that vat leaching offers,” Global Geoscience managing director Bernard Rowe said in the company’s announcement to the Australian Securities Exchange.
“The rapid leach times, lower acid consumption and lower solution requirements are expected to have a very positive impact on both capital and operating cost estimates.
“The results bode well for the soon to be released trade-off studies being undertaken as Phase 1 of the Rhyolite Ridge Pre-Feasibility Study.
“Sulphuric acid will be the largest reagent cost and reducing acid consumption will have a very positive impact on operating costs.
“Vat leaching allows for much greater control of the leaching processing resulting in faster, more efficient and targeted leaching when compared to heap leaching.
“With a vat leach, we can control temperature, acidity (pH) and solution flow rates and this provides significant advantages over heap leaching.
“This control allows a more selective leach which recovers the lithium and boron, however, does not leach as many of the other elements into solution.
“Lower levels of other elements in the PLS has the benefit of simplifying the crystallisation and purification process steps.
“On-going metallurgical testwork is concurrently evaluating various attractive options to produce lithium carbonate and boric acid on site.”
Global Geoscience reiterated its claim that the Rhyolite Ridge is the only lithium deposit in the world that has been demonstrated to be amenable to simple acid leach processing, reinforcing it as an economically viable alternative to spodumene and brine deposits as a major, low-cost and long-term source of lithium.