ASX-listed Aldoro Resources has identified for potential for a world-class rubidium deposit at its Niobe prospect in Western Australia’s Mid West. It has defined a preliminary rubidium exploration target of 33,000 to 150,000 tonnes at grades ranging from 696-1457 parts per million rubidium oxide over an area of 80m by 65m. The evaluation is based on historical drilling done in the mid-1980s by Pancontinental Mining.
The area evaluated in Aldoro’s report represents less than half the mapped section of the Niobe Pegmatite 1, indicating that the potential quantity could be considerably bigger. However, management points out that this exploration target is conceptual in nature and only an approximation.
The Niobe project is 70km north-west of Mount Magnet and contains several areas of significant lithium and tantalum enrichment. Aldoro, which has a collection of gold, nickel and lithium exploration projects in WA, has now set its sights on rubidium, an industrial metal that fetches more than A$1.4 million per tonne. The company hopes to start the drill rods spinning in late September at the Niobe project and will also target the lithium potential of the mapped pegmatites.
Aldoro initiated the re-evaluation of the Niobe prospect, which is part of the giant ultramafic-mafic Windimurra Igneous Complex, as values of rubidium oxide over one per cent were recorded from historical mid-1980s reverse circulation drill holes by Pancontinental Mining. Thirty-one close-spaced, shallow, interval holes over an area of 80m by 65m were drilled by Pancontinental between 1984 and 1986 to depths between 13m and 48m. Down hole sampling was conducted at 1m intervals and sub-samples were analysed for the lithium pegmatite suite of elements including lithium, rubidium, caesium, niobium, tantalum and tin.
Pancontinental interpreted its drilling results to indicate a shallow north dipping pegmatite sheet that plunges to the north-west, flares at surface briefly and gently tapers with depth. Drill profiles indicate a true thickness of 25m to 35m which tapers off to the north-east. The pegmatite is zoned with an outer wall zone, intermediate zone and quartz rich core. The inclined quartz core is itself zoned towards the base and most of the mineralisation occurs in the intermediate contact zone with the lithium-bearing mineral zinnwaldite which is common in the lower zone. Rubidium appears to be hosted in the zinnwaldite in this lower zone.
Tantalum was mined from the pegmatite in 1996 with 20 tonnes of tantalum heavy mineral concentrate produced from a small shallow pit with the tailings left onsite. Significantly, apart from the Niobe tantalum pit area and nine reconnaissance holes into Pegmatite 2, the pegmatite field has not been tested for rubidium, lithium or caesium.
Rubidium is a very soft, silvery-white metal and rubidium compounds are sometimes used in fireworks to give them a purple colour. Rubidium is also used in a range of industrial applications including specialty glasses in fibre optic cables, GPS systems and night vision gear, and, importantly, has the potential to be applied in sodium-ion batteries. It has a variety of biomedical uses, particularly for imaging brain tumours and can also be used to treat depression.
Two notable sources of rubidium are the rich deposits of a zeolite mineral, pollucite, in Manitoba, Canada and on the Italian island of Elba, where additionally, rubidium-bearing feldspar has rubidium contents of 17.5 per cent.
However, the recently discovered Tiantangshan tin-tungsten-rubidium deposit in the Guangdong province of China contains over 100,000 tonnes of rubidium oxide hosted in micas, at the average grade 0.109 per cent, which makes it is the biggest rubidium deposit in the world. The provincial government has announced that it will spend “multi-billion yuan” over five years to develop this deposit.
Aldoro chairman Joshua Letcher said: “It seems that the potential resources of the Niobe rubidium project of Aldoro Resources may be in the same order with the Tiantangshan rubidium deposit with analyses of rubidium oxide greater than 1.5 per cent and is associated with other valuable elements, such as lithium, caesium and tantalum.”
The company now plans to expand the exploration target area and, pending approvals, will start a reverse circulation drill program at the end of September with the aim of mining within a year. If Aldoro is on the right track, this could be a game changer for the company and the Mount Magnet district.
Is your ASX-listed company doing something interesting? Contact: matt.birney@businessnews.com.au
By Matt Birney
