The high tenor and speed of the uranium extraction suggest the Theseus mineralisation consists predominantly of uraninite and coffinite and is readily available for leaching. This is a very promising result and is comparable to preliminary recoveries from other Australian in-situ recovery type deposits. Further studies will determine the exact nature of the uranium mineral speciation.
Five Theseus drill-hole samples were combined to make a composite sample suitable for bottle roll leaching tests. The locations of the drill holes are shown on Figure 1 and the assay results for the five original and the combined composite sample are shown in Table 1. The 16.6kg composite, mineralised sample gave a head assay of 330ppm U3O8 using an XRF analytical method. The mineralised sample consists of a variety of sand, minor clay and carbonaceous material obtained from aircore and mud-rotary drilling. The laboratory technical work was completed by ALS Ammtech based in Adelaide.
In the first bottle roll test a 1kg sub-set of the composite sample was treated with H2SO4 to give an approximate pH of 1 and rolled for 48 hours resulting in a 95.5% extraction with an acid consumption of only 5.6kg/t. A second sample treated similarly with the addition of H2SO4, to give an approximate pH of 0.5, resulted in a marginally higher 96.4% extraction and an acid consumption of 20.3kg/t. No oxidant was added for either of these two tests. Achieving very high extraction rates without the need for an oxidant at this early stage is highly encouraging.
A quantitative electron microscope scan (known as QEMSCAN) carried out on one sample reports up to 83% of the uranium minerals being available for leaching, mostly coating grains and in fractures. The leach results suggest that the figure of 83% may be an underestimation. This is an important factor for the proposed in-situ mining technique for Theseus. Further studies will test extraction parameters using alkaline leaches, by adding oxidant and varying the amount of acid being used. The final results are expected in the next few weeks.
Toro's Managing Director, Mr Greg Hall, said "these initial uranium extraction tests are extremely encouraging and demonstrate good metallurgical characteristics for the Theseus Project at this early stage of the project. The Theseus Project continues to achieve milestones on a path towards an initial resource statement in the third quarter of 2012".
* "Bottle roll" leach results are a preliminary benchscale test under laboratory conditions to test for uranium extraction under controlled conditions. Recoveries do not necessarily reflect final expected metallurgical recoveries.
# An XRF assay method tends to report more accurate and reliable uranium assay results when compared to multi-digest ICP results, for results greater than 200ppm U3O8.
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About Toro Energy Limited
Toro Energy is a modern Australian uranium company with progressive project development, acquisition and growth. The company is based in Adelaide, South Australia with a project office in Perth, Western Australia.
Toro’s flagship and wholly-owned Wiluna uranium project (includes existing mining lease) is 30 kilometres southeast of Wiluna in Central Western Australia.
Wiluna contains two shallow calcrete deposits, Lake Way and Centipede, with prefeasibility and optimisation studies completed and a definitive feasibility study underway. Toro has advanced the Approvals process with an anticipated date of mid-2012, construction through 2013 and first uranium sales in 2014.
Toro has a new uranium project at Theseus in Western Australia, and owns uranium assets in Northern Territory, South Australia and in Namibia, Africa.
Toro Energy Limited