Mt Gilmore, NSW
Mt Gilmore Cobalt-Copper-Gold Project, NSW – Australia
The Mt Gilmore Cobalt-Copper-Gold Project (Mt Gilmore) is located 35 kilometres from the city of Grafton in north-eastern New South Wales (NSW), and is host to the unique, high-grade, cobalt-dominant Cobalt Ridge Deposit (Cobalt Ridge). Corazon owns an 80% interest in Mt Gilmore and is managing and sole funding exploration until any future decision to mine is made.
Much of Mt Gilmore’s historical exploration has focused on the Cobalt Ridge prospect – a rare high-grade cobalt sulphide deposit. Corazon’s metallurgical testwork on the Cobalt Ridge mineralisation has delivered exceptional, high-grade metal concentrates and cobalt/copper sulphates, suitable for use in rechargeable (lithium-ion) batteries.
Since acquisition in mid-2016, Corazon’s exploration results have underpinned its belief that Mt Gilmore is prospective for hosting multiple rare, cobalt-rich sulphide deposits, similar to Cobalt Ridge. Corazon’s recent exploration of the prospective 22 kilometre “Mt Gilmore trend” uncovered a major copper-cobalt-silver-gold geochemical trend, potentially representing a district-scale exploration play for large intrusive-related copper-cobalt-gold deposits. These targets have become Corazon’s exploration focus at Mt Gilmore.
Mt Gilmore Project location map
80% earn-in interest completed
Corazon recently completed its 80% earn-in interest at Mount Gilmore (ASX announcement 2nd July 2019). Corazon entered into an agreement with the project vendors, Providence Gold and Minerals Pty Ltd in 2016, giving it the right to earn up to an 80% interest in Mount Gilmore by completing $2 million in exploration expenditure at the project within three years of commencement of the agreement (ASX announcement 16th June 2016).
Geophysical targets identified below large surface geochemical anomalies
Corazon recently announced its initial results from its IP geophysical survey that is testing the recently identified copper-cobalt-silver soil anomalies (ASX announcements 23 July 2019). The newly identified areas of mineralisation are believed to support the potential for a large concealed sulphide system (ASX announcement 31st May 2019).
Importantly, these newly identified areas of mineralisation are adjacent to the high-grade copper rich structures previously identified by Corazon (ASX announcement 5 February 2019), and are believed to represent a mineralised alteration halo of what may potentially be a large, concealed sulphide system.
IP methods have been used with great effect in the successful exploration for sulphide deposits in NSW.
Corazon’s current IP survey at Mt Gilmore is a first-pass, wide-spaced program which provides an initial test of the effectiveness of IP, testing for geophysical characteristics typical of concealed copper-cobalt-gold sulphide bodies.
To date, the IP survey results have been extremely encouraging. The Gordonbrook Hill (GBH) target is the best IP anomaly identified to date, exhibiting moderate changeability anomalism over an area of approximately one (1) kilometre in diameter. In addition, mapped “leakage structures”, adjacent to and extending from the GBH target have previously returned rock chip sample results of up to 16.3% copper, 1,250 ppm cobalt and 1.29 g/t gold (ASX Announcement 5 February 2019), which reinforce this target area’s strong prospectivity.
Mt Gilmore Project – interpreted regional geology over copper in soils
The IP survey has defined large areas of moderate “IP changeability” anomalism, interpreted to be hydrothermal alteration and sulphide mineralisation in association with high “IP resistivity” areas, interpreted to be intrusive bodies. This relationship is supported by Corazon’s field mapping at Mt Gilmore (Figure 3).
IP surveys are typically utilised for identifying the presence of mineralisation at depth; however, at Mt Gilmore the correlation of the IP results at shallow depths with mapped geological features at-surface has delivered a very positive outcome for Corazon. It is expected priority targets for the Company’s next round of drilling will be defined from this work.
Discovery of major new Copper-Cobalt-Silver-Gold trend
In the March 2019 quarter, Corazon announced the discovery of a major copper-cobalt-silver-gold trend at Mt Gilmore (ASX announcement 5th February 2019). Multiple, large (+1km) priority surface (soil) geochemical anomalies were discovered within the currently defined 22 kilometre-long mineralised Mt Gilmore Trend.
Initial field reconnaissance of the anomalous copper-cobalt-sliver trend at Mt Gilmore has identified several areas of hydrothermal alteration and disseminated sulphide mineralisation at surface. Sulphides observed include extensive disseminated pyrite, pyrrhotite and chalcopyrite (copper sulphide) – consistent with the geochemical anomalism identified by the Corazon’s soil sampling program.
This exploration work has proven to be highly effective in mapping alteration and mineralisation at Mt Gilmore and provides compelling evidence of an extensive hydrothermal event with metal associations indicative of large intrusive related copper-gold systems.
Corazon’s assessment that the numerous occurrences of copper-cobalt-gold mineralisation identified in late-1800’s/early-1900’s small scale mining operations may in fact be part of a much larger system represents a significant advancement for Mt Gilmore, substantially increasing its potential.
The new, high-tenor cobalt-copper-silver-gold soil sample anomalies are supported by high-grade rock chip samples (ASX announcement 22nd November 2018). Better results include up to 21.6% copper, 1,795ppm cobalt, 1.29g/t gold, 361ppm silver and 885ppm molybdenum. The structures hosting this mineralisation are interpreted to be “leakage-structures” from a concealed copper sulphide system.
This newly identified Mt Gilmore geochemical trend represents a district-scale exploration play for large intrusive-related copper-cobalt-gold deposits and provides Corazon with a unique early-stage copper-driven opportunity.
Metallurgical testwork – battery grade Cobalt produced
Corazon’s highly successful Phase 3 metallurgical testwork delivered a high grade cobalt concentrate with the potential to supply the emerging global battery technology sector.
The Phase 3 metallurgical testwork focused on defining down-stream concentrate processing options. The results have successfully demonstrated exceptional recovery rates of cobalt, copper and gold from drill samples from the Cobalt Ridge Deposit, using conventional processing routes.
Conventional flotation testwork delivered a high-grade cobalt-copper-gold concentrate – of up to 7.38% Co – from high grade Cobalt Ridge samples, as well as excellent concentrate grades from lower low-grade samples (see Table 1 below).
Table 1: Phase 3 metallurgical sample and concentrate grade
The combination of high grade concentrates and very high recoveries delivered in the testwork provides Corazon with the opportunity to potentially either produce a high-value bulk concentrate for direct sale, or to develop an in-house down-stream processing plant.
Corazon produced high-grade concentrates from simple flotation processing, with solvent extraction following standard pressure oxidation (POX), to deliver separate high-quality cobalt and copper sulphates. Gold is captured separately from the POX residue.
The mineralisation at Cobalt Ridge has several beneficial characteristics. A key advantage for the processing is the sulphide mineralisation at Cobalt Ridge, which allows for a smaller sulphide/metal concentrate to be produced prior to down-stream processing. This would likely significantly reduce the capital and operating costs of a down-stream plant, compared to having to process a bulk feed.
Phase 3 Testwork – pressure oxidation confirmed as preferred processing route
Down-stream testwork focused on the use of pressure oxidation (POX) as the method for cobalt and copper extraction. POX was identified as the preferred process route due to its potentially lower cost, processing adaptability for variable mineralisation and its capacity to deliver environmentally stable and controlled waste products.
The POX testwork achieved excellent results, with up to 98.91% cobalt and 96.70% copper extraction. The solution from the POX underwent precipitation testing in order to assess metal removal, with solvent extraction testing being completed using conventional organics.
The solvent extraction shake tests were performed in three successive stages: copper solvent extraction, impurity solvent extraction and cobalt solvent extraction. The copper was selectively extracted from the liquor, with >99% of the copper removed from the solution. Cobalt solvent extraction proved successful, with >99% of the cobalt extracted.
The copper and cobalt stripped solutions were further concentrated to levels that allowed for product generation. The concentrated copper solution produced a light blue powder, suggesting a hydrated copper sulphate (CuSO4•xH2O). This powder underwent ICP analysis, which indicated the copper sulphate had a purity of 98.0-98.2% based on the impurities measured and detected. Future solvent extraction optimisation work is expected to improve the quality of the copper sulphate product.
The concentrated cobalt solution produced a pink powder suggesting a hydrated cobalt sulphate (CoSO4•xH2O) (Figure 1). The pink colour of the powder indicated the material may be predominantly monohydrate (34% Co) as opposed to heptahydrate (21% Co), which has a much deeper red colour. Either product is achievable. The cobalt sulphate product had a purity of 99.8-99.9% based on the impurities measured and detected.
The residue from a large scale POX test, which contained 3.39 g/t gold, underwent bulk leach extractable gold (BLEG) testing. Analysis of the BLEG results indicated that 99.9% of the gold was recovered on an assayed head-grade basis.
The testwork was managed by internationally recognised metallurgical consultants, METS Engineering (see competent person statement below) and independently carried out at ALS Metallurgy in Balcatta, Western Australia.