Highlights
- Outstanding Independent Metallurgical test work results from Revere Gold Project samples
- Gold grade of 305g/t in 41kg bulk quartz vein sample and 3.7g/t from 59kg siltstone host rock sample
- Coarse free gold picked from quartz vein sample accounts for 47% of gold in quartz sample
- Gravity Gold Recovery of 97% (excluding picked coarse gold) to primary gravity concentrate from quartz vein sample to very high grade primary concentrate of almost 50kg/t
- Gravity Gold Recovery of 92.8% to primary gravity concentrate from siltstone host rock sample to primary concentrate grading 4,323 g/t
- EMC commences planning for low-cost, simple crushing-grinding-primary gravity concentration processing circuit
Commenting on metallurgical results of the Revere Gold Project, Executive Chairman & 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. We look forward to further progressing the exciting Revere Gold Project over the coming quarters.”
Everest Metals Corporation Limited (ASX: EMC) (“EMC” or “the Company”)is pleased to announce the results of initial metallurgical test work conducted on two samples of mineralised rock material from the Revere Gold Project (“RGP”) located 90km NE of Meekatharra, in the Mid-West region of Western Australia.
The test work program reinforces the high nugget gold attributes of the deposit, with 305g/t Au in the quartz vein sample of which 47% is in visible coarse gold. It also achieved high recoveries of 97% and 92.8% to a primary gravity concentrate from both the quartz vein sample and the host rock siltstone sample.
Background
The Revere Gold Project is 82km2 and includes granted tenements E51/1766, E51/1770, P51/3240, P51/3241 and pending applications M51/905, E51/2119, E51/2088. EMC has the right to earn up to a 100% interest[1] in tenements.
The project is located just off the Great Northern Highway approximately 90km to the north-east of Meekatharra in the Murchison Region of Western Australia and sits proximal along the interpreted northern extension of the Andy Well greenstone shear system in proximity to the prospective NE-trending Goodin fault zone (Figure 1). This fault zone is being actively explored for high grade massive sulphide copper mineralisation similar in style to DeGrussa Mine, located 55km to the north-east of the Revere project. This metallogenic zone has numerous mesothermal-style gold stockwork systems and has produced numerous coarse gold nuggets from quartz reefs over the past 100 years.
Metallurgical Testwork
To further investigate the potential of a high nugget gold distribution, bulk samples were collected from a shallow prospecting pit (costean) in the Revere Reef system located in tenement E51/1766 and pending mining applications M51/905 (Figure 2). The samples provided to the independent laboratory for Gravity Recoverable Gold (“GRG”) test work, comprised two distinct samples: one from the main quartz vein (sample 03196) and one from its siltstone host rock (sample 03197).
The test work was undertaken by Nagrom Metallurgical Laboratories in Perth, WA. The program consisted of sample preparation, crushing, removal of coarse visible gold, size by assay analysis of the crushed ore, and Gravity Recoverable Gold determination through three stages of gravity gold recovery in a Knelson Concentrator (“KC”)[2]. The tailings from each stage of the Knelson Concentrator gravity separation was ground finer prior to the next stage of gravity separation.
Coarse, visible gold (Figure 3) was removed from the quartz vein sample (sample 03196) prior to subsequent size by assay analysis and gravity separation. Average and replicate assays on the two samples crushed to below 2mm show that the quartz vein sample averaged 161 g/t (Table 1). Accounting for the coarse visible gold that had been picked from this sample, on the basis that it is 24 carats, increases the gold grade in this sample to 305 g/t. The host siltstone sample averaged a gold grade of 3.7 g/t.
Table1 – Samples Head Assay
| Sample | Mass (kg) | Au (Calc) | Replicate 1 Au (ppm) | Replicate 2 Au (ppm) | Replicate 3 Au (ppm) | Replicate 4 Au (ppm) |
| 03196 | 40.8 | 161.349 | 149.427 | 203.281 | 155.170 | 137.517 |
| 03197 | 58.6 | 3.743 | 8.399 | 1.403 | 1.056 | 4.115 |
The samples were then ground to a coarse 90% passing size of 0.85mm for primary gravity separation. The primary concentrate tails were reground to a 50% passing size of 75 microns prior to secondary gravity separation. The secondary concentrate tails were reground to a 80% passing size of 75 microns prior to a third stage of gravity separation, again in a Knelson Concentrator. The Gravity Recoverable Gold testwork results are summarised in table 2.
Table 2 – GRG Testwork Results of Revere bulk samples
| Sample | Fraction Stage | Weight (%) Au | Au (ppm) | Au Distribution (%) |
| 03196 (Quartz vein) | Primary Knelson Concentrate | 0.42 | 49,996 | 97.00 |
| Secondary Knelson Concentrate | 0.39 | 865 | 1.56 | |
| Tertiary Knelson Concentrate | 0.36 | 171 | 0.28 | |
| Tertiary Knelson Tailing | 98.83 | 2.55 | 1.16 | |
| 03197 (Siltstone host) | Primary Knelson Concentrate | 0.37 | 4323.7 | 92.83 |
| Secondary Knelson Concentrate | 0.35 | 119.9 | 2.38 | |
| Tertiary Knelson Concentrate | 0.35 | 35.95 | 0.72 | |
| Tertiary Knelson Concentrate | 98.93 | 0.71 | 4.07 |
The quartz vein sample (03196) showed excellent gravity gold recovery of 97.0% to a very high-grade primary concentrate (~50kg/t) with the Knelson Concentrator fed with a coarse feed (P90 of 0.85mm). Substantially finer grinding (to ~75 microns) prior to secondary and tertiary gravity separation increased the gold recovery by 1.8%. The siltstone host sample (03197) also resulted in high recovery to the primary concentrate (92.8%) although the concentrate is lower grade. The gold distribution in the primary concentrates of the two samples is very similar (Figure 4).
This testwork program highlights the high nugget distribution of gold in the Revere Gold Project. It also shows the potential for a simple, gravity gold circuit to process Revere ore at a coarse grind size, which will minimise project capital and operating costs.
A summary of important assessment and reporting criteria used for this Exploration Results announcement is provided in JORC Table 1 in accordance with the checklist in the Australian Code for the Reporting of Exploration Results, Mineral Resources, and Ore Reserves (the JORC Code, 2012).
The Company intends to commence a trenching program for supplementary bulk sampling and mapping of the reefs system in the June 2023 quarter and a deep drilling program to delineate the extent of the high-grade gold mineralisation in the Revere reef. An additional metallurgical testwork program is planned from the bulk samples in the new areas to further evaluate gold production using a simple gravity gold circuit for processing Revere ore.
NEXT STEPS
- Bulk sampling, additional metallurgical test works and deep diamond drill program to commence in Q2-2023
[1] ASX: EMC; EMC To Acquire Up To 100% Of Revere Gold Project, dated 11 January 2023
[2] The Knelson Concentrator is a vertical axis bowl-type centrifugal concentrator that uses a fluidized bed to perform its concentrating duty. Knelson is an essential unit operation in any gold processing plant to assess the gravity recoverable gold content in the ore as well as to recover fine free gold from the grinding circuit.
