THE BOURSE WHISPERER: Middle Island Resources (ASX: MDI) declared it had received “exceptional results” from a preliminary metallurgical testwork program undertaken on the Two Mile Hill tonalite deeps mineralisation at the company’s 100 per cent- owned Sandstone gold project in Western Australia.
Middle Island said recent metallurgical testwork results had indicated gold recoveries of 93 per cent to 97 per cent for the Two Mile Hill tonalite deeps mineralisation at the Sandstone gold project.
The testwork, undertaken by Australian Laboratory Services (ALS) in Perth, used continuous intervals of diamond drilling core that were submitted to make a ‘ROM composite’ for gravity gold recovery (GRG), followed by leach testwork.
A bond ball mill work index test was also undertaken on additional diamond core.
Middle Island said the testwork had demonstrated over 58 per cent of gold is recoverable via gravity concentration prior to leaching with the leach testwork exhibiting rapid leach kinetics, with 90 per cent of total gold extraction achieved within the first two hours on run-of-mine (ROM) composite samples following gravity gold recovery.
The bond ball mill work index (16.4kWh/t) confirmed ore amenability for treatment through the Sandstone mill.
Middle Island indicated that with more than 58 per cent of the gold recoverable via gravity concentration in laboratory testwork, the Sandstone treatment plant gravity circuit will be utilised when treating ore derived from the tonalite deeps deposit.
The company anticipates future plant gold recoveries from the tonalite deeps to match historic recoveries from the Two Mile Hill oxide material treated late in the 1990s.
Further drilling is underway at the Two Mile Hill deposit to extend a previous hole that ended in mineralisation at 498.9m depth, with an intercept of 66.9m at 3.27g/t gold to at least 850m, and potentially up to 1,000m depth.
In addition, reverse circulation percussion (RC) pre-collared diamond drilling will also assess up-dip extensions of high-grade, BIF-hosted gold mineralisation, which includes a best intercept of 22m at 23.8g/t gold (true width), adjacent to the Two Mile Hill tonalite.
“While the Two Mile Hill tonalite deeps mineralisation was anticipated to be metallurgically benign, these results confirm and, indeed, exceed our expectations,” Middle Island Resources managing director Rick Yeates said in the company’s announcement to the Australian Securities Exchange.
“This is particularly the case with respect to the high gravity recoverable gold and the rapid leach kinetics demonstrated by the testwork.
“The modest bond work index of 16.4kWh/t is also an exceptional result, no doubt due to the ameliorating influence of the pervasive sericite-carbonate alteration within the tonalite.
“Equally, the low indicative reagent (cyanide and lime) consumptions represent a significant bonus.
“While this testwork program is preliminary in nature, the consistency of the tonalite-hosted mineralisation is such that we would not reasonably anticipate any significant deviation in any future testwork.
“The results also serve to vindicate the company’s decision to extend diamond hole MSDD156 from 500 metres to at least 850 metres depth, and potentially as much as 1,000 metres depth.
“The result also provides the confidence to progress further drilling and studies on what is evolving into a substantial, well-mineralised target.”