Everest Metals’ early exploration mapping, rock-chip sampling and first-phase reverse=circulation (RC) drilling has identified potentially world-class lithium-caesium-tantalum (LCT) mineralisation in an extensive pegmatite field at its Mt Edon project, about 5km south-west of Paynes Find in Western Australia’s Mid West region.
Reconnaissance work earlier this year included mapping in March and a DGPR survey in April. Additionally, 10 rock-chip samples were taken and submitted for assay and mineralogical studies, yielding startling results of up to 3.1 per cent rubidium, 4.6 per cent lithium and 0.34 per cent caesium.
All except two of the rock samples are considered indicative of highly-fractionated and high LCT-fertility pegmatites and are the highest-grade surface rock-chip samples unveiled from Mt Edon when compared with the nine previous surface samples reported from the area last year.
Everest Metals chief operating officer Simon Phillips said: “We are very excited with the assay results from such a small drilling campaign. The hunt for the source of this recently discovered LCT mineralisation continues with the proposed stage-2 drilling campaign set to commence in early August 2023.”
Geologically, the project lies in the southern portion of the Paynes Find greenstone belt – a north-east-trending sequence of mafic, ultramafic and sedimentary rocks, all cut by east-west trending structures.
The greenstones have been intruded by several big, irregularly-shaped felsic pegmatites that have been prospected, explored and mined at various times over at least the past 50 years for gemstones, tin and tantalite and more recently for rare earths and related minerals.
Separate exploration company reports in 1970 and 1971 noted pegmatites in several locations near Paynes Find and referenced tantalum and other rare earths. But the occurrences were not followed up due to other commodity interests.
Pegmatites within Everest’s project area comprise interconnected folded sills dipping in various directions at various angles. They have a north-east/south-west length along strike of up to 350m and occur along a 1.2km stretch of what is now termed “the LCT Pegmatite Corridor”.
Everest’s surface reconnaissance work earlier this year was followed up with a small drilling program comprising 441m of RC drilling in 11 holes and arrayed across nine targets, with average hole depths of 40m. The program was completed in late May. Geological logging of chip samples showed moderate-to-strong fertile pegmatite mineralisation and abundant, well-developed muscovite-rich zones.
All but one of the drillholes intersected solid runs in pegmatites, with the best intercepts including a 15m pegmatite from 4m to 19m, a 14m pegmatite from surface to 14m, a 15m pegmatite from 4m to 19m and a 62m pegmatite from 49m to end-of-hole at 111m that finished in pegmatite. There was also an 8m pegmatite from 22m to 30m, 7m from 32m to 39m, a 27m pegmatite from 6m to 33m and 29m from 1m to end of hole at 30m that also finished in pegmatite.
The company’s best results from its drill program include an excellent run of high-grade rubidium reported in one hole as 40m at 0.26 per cent rubidium from 49m, including 19m at 0.33 per cent rubidium and 0.1 per cent lithium from 51m, in addition to 2m at 0.23 per cent rubidium from 1m and 2m at 0.3 per cent rubidium from 4m.
The entire mineralised intersection within the hole appears to confirm the highly-fractionated status and fertility of the pegmatite in the north-east corner of the project. The pegmatite body in the hole remains open below 111m, with the potential for lateral extension – particularly towards the north-east.
Encouragingly, the drillhole is collared in the same spot where high-grade rock-chip samples were taken, assaying up to 3.1 per cent rubidium and 4.6 per cent lithium and which is thought to have the potential for high-grade LCT pegmatite at depth. The drilling program also identified multiple pegmatites with LCT potential at considerable downhole depths of up to 111m within the 1.2km “pegmatite corridor”.
Everest’s high-grade rubidium intercepts are totally in line with other world-class occurrences, including the Karibib pegmatite deposit in Namibia that features 8.9 million tonnes at 0.23 per cent and the Guobaoshan deposit in China that has 23 million tonnes at 0.12 per cent.
The current ascendency of the rubidium market lies in its potential use as a component in sodium-ion batteries, the manufacture of photocells and in the removal of residual gases from vacuum tubes.
Rubidium salts are used in glasses and ceramics, and in fireworks. Rubidium carbonate has multiple industrial uses, principally for speciality glass such as fibre optic cables, telecommunications systems – including a key role in GPS systems – and night vision devices.
Moreover, the escalating demand for rubidium in biomedical research is expected to propel market growth. The present price of rubidium carbonate is currently more than $1100 per kilogram, placing it among the most valuable of critical metals.
Everest will follow up its successful program with a second phase of RC drilling next month in a bid to define the lateral extension of high-grade zones in the north-east corner of Mt Edon and to evaluate other as-yet undrilled pegmatites.
The company also proposes to undertake vital mineralogical studies to properly characterise the mineral assemblage of its LCT pegmatites.
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By Doug Bright
