Everest sees avenue to revenue in Revere bulk gold sampling
Everest Metals may soon be about to join the ranks of gold producer at a time of record high gold prices after months of work at its Revere project with the arrival of a mobile Gekko Gravity processing plant which is now on its way to site.
The ten tonne per hour Gekko plant is intended to initially treat up to 36,000 tonnes of bulk sample material along a high-grade section of the Revere reef system.
The company already has an 8000 tonne parcel of gold-mineralised bulk sample material crushed to passing 5mm during its Phase-1 bulk sampling campaign between August and September.
That parcel is now stockpiled ready to feed the new plant once it is set up on site and commissioned. The necessary site, civil and earthworks have already been completed in time to receive the plant. The Gekko system is designed to produce a gold concentrate, which will provide revenue from the bulk sampling program.
Three test bulk sample sites have been selected along an 700m-long section of an established exploration target which is part of the 7km-long Revere gold-rich shear and reef system and will help the company identify the extent and nature of the mineralisation in just a small section of the reef.
The reef system is characterised by high-grade gold vein and stockwork occurrences which are surrounded by an extensive halo of low-grade mineralisation and which, from current investigations, can be up to 130m deep, leaving plenty of scope for resource expansion
The location of the sample pits was designed to provide geo-metallurgical variability data and to confirm other geological assumptions relating to the project.
Everest says that its own review of reconciled grades from historical processing of quartz lodes showed they could vary considerably, between an impressive 17g/t and up to, incredibly, 325g/t gold. And because “historical processing” implies a parcel of material of some size, the true variability of smaller sub-samples within the parcel could be even greater.
Such extreme variations – the bane of gold miners for almost as long as the precious metal has been processed – comes about because of the well-known “spotty” nature of gold distribution, otherwise known as “nugget effect” which may exist in some deposits.
The company recognises the issue at Revere and has grabbed the spotty bull by the horns with the goal of the bulk sampling program being to identify, reconcile and statistically “iron out” the grade peaks caused by nuggety gold.
The primary objective of the sampling program is to provide a reliable and reproducible suite of “average” grades for the company’s future resource block-modelling for full-scale mining which can be used with confidence within a particular mineralised zone.
With the recent gold price curve on every chart seemingly heading for the stratosphere, Everest has grasped a somewhat unique opportunity to undertake the bulk sampling exercise in a resource known to be subject to nugget effect and which would come in ahead of future mine planning, mining and processing and could ultimately influence final plant circuit design.
Not insignificantly, the company is also looking towards some real financial reward – or at least recompense – from the procedure and end up better-informed to deal with and profit from the problem before finalising its resource modelling over a bigger resource target area.
This could be far better and potentially much cheaper than drilling the daylights out of the resource at close spacing with no guarantee of solving the problem, while still risking the attendant high costs of drilling, analyses and other add-on costs that would all be going one way … out of the company’s pocket.
The other key aspect of the process is that if coarse and nuggety gold is a potential problem, then it seems eminently smarter to use a gravity gold processing plant to trap it early and then treat the remaining fine gold component through a more conventional chemical pathway – subject to metallurgical feasibility.
Removing excessive coarse gold from any conventional leach circuit can increase cyanide use and may even extend the leach residence time required to ensure total gold dissolution.
The degree to which this could be a problem depends on the maximum gold particle size expected, so sizing analyses are also important.
Gold is also known to settle, lodge or accrete anywhere in a plant where it can often remain for some time. Pulling the coarse gold out early into a secure sub-circuit would seem to make a lot of sense.
Extensive metallurgical work by the company has already shown that high grade recovery is possible through primary gravity concentrate production.
The imminent mobilisation of the Gekko Gravity Plant allows for the commencement of processing of high grade and low grade mineralised stockpile, taking advantage of the record high gold prices and helping to monetise our development. This is an exciting step as we work towards our inaugural JORC MRE for the project. The recent expansion of our tenement holdings at Revere with the granting of an additional 84km2 exploration licence continues to consolidate our footprint of this highly prospective area.
The 171 sq km Revere project lies about 90km north-east of Meekatharra in WA’s Murchison Region, about 900km north of Perth and is situated along strike from the impressive DeGrussa and Monty Copper-Gold mines.
The Revere reef system comprises a series of high-grade gold reefs within a north-east trending structural corridor which encloses a prominent aeromagnetic trend.
Some of the reefs share characteristics reminiscent of the famed Victorian saddle-reefs such as those at Bendigo which are also renowned for nugget gold occurrences and have produced a cumulative output of more than 60 million ounces of gold.
In late 2023, Everest applied for a key exploration licence at the Revere project which was granted just in the past couple of weeks.
It was only a year ago when Everest first reported a maiden exploration target range for Revere ranging between 2.5 and 4.1 million tonnes in a grade range between 1 and 2.5g/t of gold.
The target range was based on historical drilling data over an area measuring about 800m long and 150m wide and 194 RC holes drilled in 2018 by Mineral Commodities for a total of 8845m and 1997 samples analysed for gold.
Everest completed its Phase 2 drilling and blasting in mid-September, for a total of 2090m of drilling of 209 precisely-spaced holes, with each hole drilled to 10m. The analytical results have been returned but are still subject to compilation and interpretation.
Everest’s months of work on setting up and running a well-controlled bulk sampling program offers a rare opportunity to learn a lot about the Revere deposit and high-grade gold deposits more generally.
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