Everest Metals has achieved exceptional gold recoveries from independent gravity separation metallurgical test work from its Revere gold project 90km northeast of Meekatharra in Western Australia. Coarse gold hand-picked from the 41kg bulk quartz vein sample accounted for 47 per cent of the recovered gold. The bulk quartz sample had a head grade of 305 g/t gold and gravity separation recovered 97 per cent of the gold remaining.
On the strength of the results Everest is now planning a low-cost crushing, grinding and gravity separation processing facility at Revere pending similar results from an already permitted 36,000 tonne bulk sample and further drilling.
Gravity separation testing of a 59kg sample of siltstone host rock to the quartz veins, grading 3.7 g/t gold, recovered 92.8 per cent of the gold. The primary gravity concentrate from the siltstone graded 4,323 g/t gold.
Using a Knelson concentrator the quartz ore sample yielded a very high primary concentrate grade around 50 kg of gold per tonne.
Everest Metals Executive Chairman and Chief Executive Officer, Mark Caruso said: “These metallurgical results highlight the high-grade nature of mineralisation. The very high recoveries to a primary gravity concentrate at a coarse grind size for both the gold bearing quartz vein and the surrounding host siltstone are especially pleasing as they facilitate processing in a simple gravity circuit.”
Everest believes the test work further demonstrates the high nugget gold attributes of the Revere gold deposit. The deposit lies on a northern extension of the Andy Well gold mine and is hosted on a greenstone shear system. The northeast trending zone is being explored for high-grade massive sulphide copper mineralisation similar in style to Sandfire’s DeGrussa copper mine, located 55km to the north-east of the Revere project. The metallogenic zone has numerous mesothermal-style gold stockwork systems and has produced numerous coarse gold nuggets from quartz reefs recently and over the past 100 years.
The Revere gold project is located on 82 square km of tenements and is subject to an earn-in joint venture between Everest and privately-owned mining company Entelechy Resources. Everest has already earned a 51 per cent interest and is working toward 90 per cent ownership.
The Revere project is located 50km northeast of the Andy Well gold mine which has produced over 100,000 ounces of gold per annum and has a current resource of 505,000 ounces of gold at a grade of 8.6 g/t gold. Further northeast from Revere is the and 10-million-ounce Plutonic gold endowment. Plutonic once produced over 300,000 ounces of gold per year with 6 million ounces of gold production and similar amounts of unmined resources. Catalyst’s Trident deposit further along trend has a resource of 540,000 ounces at 8 g/t gold. The Revere project sits in the middle of several large and high-grade gold endowments and a highly prospective volcanogenic massive sulphide copper zone.
Everest undertook the metallurgical test work to characterise the potential distribution of the high levels of nugget gold at the project. Bulk quartz ore and host rock siltstone samples were collected from a trench located in a pending mining lease application over the project.
The metallurgical testing process consisted of sample crushing, removal of visible coarse gold by hand, an assay of remaining different size fractions and gold recovery using a Knelson concentrator. Tailings waste from each stage of the three-stage concentrator was ground finer before further gravity separation. Assays from the samples crushed to 90 per cent passing 2mm gave a quartz ore grade of 161 g/t gold which increased to 305 g/t once the hand-picked coarse gold was accounted for.
Everest argues the gravity gold recovery from the quartz ore sample was excellent at 97 per cent when the concentrator was fed with a coarse feed of 90 per cent passing a 0.85mm screen. Secondary and tertiary grinding and gravity separation increased the gold recovery by a further 1.8 per cent.
Everest says the testing highlighted the high nugget gold distribution and the potential for a simple gravity gold circuit to process Revere ore at a coarse grind size which will minimise project capital requirements and operating costs.
The company will now undertake additional bulk sampling and metallurgical testing in the second quarter of the year in addition to a deep diamond drilling program to delineate the high-grade gold resources at Revere while volcanogenic massive sulphide copper-gold will be targeted at depth. Finally, bulk ore samples will be tested from new areas to further evaluate the gravity processing option.
The nearby DeGrussa copper deposit was a company maker for Sandfire and with Everest arguing that shallow drilling has shown strong copper potential at depth, all eyes will be on this year’s progress.
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By Matt Birney
