In the first of Bulls N’ Bears’ new weekly series, “Doug Bright’s Greatest Hits”, our senior analyst gets the dirt under his well-worn fingernails to pull apart some of last week’s most intriguing ASX finds. The column will run the rule each week over a range of commodities, geological successes, oddities and matters of processing and metallurgical interest.
Many resource stories don’t always make it into the mainstream news and not everyone looks at the ASX announcements.
But some ventures deserve recounting, even if only to showcase what Aussie miners are up to at home and around the globe – and their sometimes unique innovations or discoveries. We might be relatively small in number, but here Down Under, we punch well above our weight.
Take Perth-based iron ore explorer and developer Equinox Resources, for example. Its significant recent rare earths results from a maiden sampling program at its Mata de Corda project in Brazil are certainly worth a thorough look.
Initial channel sample assays were described by management as exceptionally high results in a “frontier, district-scale discovery” up to 5024 parts per million total rare earths oxide (TREO) in clays. The 847-square-kilometre project is in the province of Patos de Minas, in Brazil’s premier exploration and mining State of Minas Gerais.
Management says more than 10 square kilometres of the area sampled yielded results higher than 2000ppm TREO in clays at surface, prompting it to ponder a new-frontier greenfield province with the potential to host a big, high-grade ionic adsorption clay (IAC) deposit.
The results reflect some near-surface depletion in an oxidised clay horizon, but show grades improving with depth, as revealed in some shallow drilling.
While the grades found are exceptional on their own accord, the fact that samples were taken from the surface oxidised clay layer, which is mixed with humic material, dramatically elevates the significance of the results and the project’s prospectivity. And future drilling could be expected to unveil significantly higher grades at greater depths in the weathered clay layer.
It is of material interest that the entire region has never been explored for rare earths, so Mata da Corda could just find itself on par with the best projects found around the globe.
And all this has been achieved within just four months of the company staking the ground.
Argent Minerals also grabbed this columnist’s attention when it unveiled its latest suite of drilling results, which it says has expanded the mineralised footprint to the north-east at its Kempfield polymetallic deposit in NSW.
The company plugged in 12 reverse-circulation (RC) drillholes at Kempfield, intersecting shallow, broad and thick high-grade zones of silver-lead-zinc mineralisation up to 88m from surface from the Western Lode area and 29m of thick, high-grade silver-base metal mineralisation north-east of the Lode 200 resource area.
The 1036m campaign was aimed at extending and defining new silver-lead-zinc mineralisation zones from the Lode 200 mineralised block and to drill-test its western zone. Significant grades from the north-eastern extension include 23m at 34.41 grams per tonne silver from 22m in one hole and a second hole intersecting 29m at 34.09g/t silver, 0.14 per cent lead and 0.41 per cent zinc from 50m including 10m going 0.31 per cent lead and 0.81 per cent zinc from 64m.
Notable grades from the western zone include one hole intersecting 0.19 per cent lead and 0.17 per cent zinc from surface and 6m running 21.97g/t silver, 0.64 per cent lead and 0.68 per cent zinc from 81m in one hole, A second hole nailed 88m at 25.23g/t silver, 0.1 per cent lead and 0.08 per cent zinc from 2m.
Argent’s flagship Kempfield polymetallic project is 60km south/south-west of Cadia’s giant gold and copper mining operation in central-west NSW, 250km west of Sydney.
Also in NSW, following an extensive recent infill drilling program, West Perth-based gold exploration and production company Alkane Resources revealed an eye-catching revision of its inferred and indicated resource for its Kaiser copper-gold project in the Boda district of NSW, which has increased management’s confidence in its resource base.
The new evaluation lifted Kaiser up to an impressive 213 million tonnes at 0.55g/t gold equivalent for 3.74 million ounces, based on average grades of 0.28g/t gold and 0.20 per cent copper and yielding a contained 1.9 million ounces of gold and 0.42 million tonnes of copper. The new numbers have raised the indicated resource category at Kaiser to 89 per cent of the overall resource, the gold grade by 15 per cent and its copper grade by 10 per cent.
Alkane says that including Kaiser, the Boda district has a global resource amounting to 796 million tonnes at a grade of 0.58g/t gold equivalent for 14.7 million ounces, based on average grades of 0.33g/t gold and 0.18 per cent copper for a contained 8.3 million ounces of gold and 1.5 million tonnes of copper.
The company has undertaken substantial metallurgical testwork and established a simple functional flowsheet, with overall recoveries at Kaiser of 81 per cent for copper and 71 per cent for gold and at Boda, 87 per cent for copper and 81 per cent for gold, with a saleable concentrate.
The company will use its revised Boda District resources in a scoping study for potential development and it is expected to be released in the second quarter of the year.
West Cobar Metals last week produced its maiden scandium resource estimate for its Salazar critical minerals project at Newmont, 120km north-east of Esperance in WA.
The company’s latest JORC-compliant inferred scandium resource estimate sits at 12 million tonnes at 103ppm and it says its preliminary metallurgical testwork indicates high scandium leach recoveries of up to 81.2 per cent.
The Salazar project is one of the most advanced clay-hosted critical minerals projects in Australia, containing significant indicated and inferred rare earths mineral resources, in addition to inferred mineral resources of titanium dioxide and alumina.
Almost all scandium was produced by electrolysis until about 1960 and at about the same time, it came to be used by the United States and Soviet Union militaries during the Cold War period because of its lightness, high melting point and resistant properties.
Prices for 99.99 per cent pure scandium have fluctuated between US$4000 (AU$6085) per kilogram and US$20,000 (AU$30,424) a kilogram in the past decade.
And finally, Larvotto Resources’ recent metallurgical engineering studies and testwork showed the company could double the original throughput of its Hillgrove antimony-gold treatment plant at Hillgrove near Armidale in NSW to more than 500,000 tonnes a year, with only minimal upgrades and modification.
The company says its capacity to produce gold concentrate and doré in conjunction with antimony concentrate could easily be increased by expanding the crusher feed rate from 220,000 tonnes per year. A complementary scoping study of historical gold and antimony production also revealed that a higher-grade gold concentrate could be produced by incorporating a new gravity separation module into the process stream, with the potential to produce a high-grade gold concentrate of more than 150 grams per tonne gold.
The potential improvement in gold output contrasts sharply with historical concentrate grades from prior operations, which produced only 50g/t gold. Management says that independent studies showed that even with the original Knelson concentrator – long regarded as the ultimate gold “catch-all” module to pick up gravity recoverable gold – in front of the flotation circuit, the original Hillgrove concentrates still retained about 13 per cent gravity-recoverable gold, most of it bigger than 40 microns (0.04 mm) in size.
Additionally, about 44 per cent of the remaining fine gold was smaller than 40 microns.
All this meant that the Knelson wasn’t catching all the gold it should have, almost certainly due to gold fineness.
Testwork also showed further improvement in the gravity gold recovery circuit would be possible using a multi-gravity gold separator (MGS), which is a more recent, less complex and less sensitive innovation than the Knelson concentrator. Management says the MGS is capable of recovering more than 70 per cent of the gold from the concentrate.
Is your ASX-listed company doing something interesting? Contact: matt.birney@businessnews.com.au
