Outstanding Cobalt Metallurgical Results (ASX announcement 7th March 2017)
- First pass flotation testwork recovers 92.2% of the cobalt, 89.0% of the copper and 75.5% of the gold in 11.1% of mass
- Concentrate graded at 7.38% cobalt, 1.29% copper and 4.1 g/t gold
- Testwork completed on reverse circulation drill chips – improvements expected
- Cobalt and copper present as sulphide minerals, gold associated with sulphide
- Viable production of a bulk concentrate for processing and separation
Corazon was recently pleased to announce that preliminary metallurgical testwork completed on samples from the Cobalt Ridge prospect, located within the Mount Gilmore Project (“Project”) in New South Wales, had delivered excellent results.
Simple flotation testing has yielded a recovery of 92.2% for cobalt, 89% for copper and 75.5% for gold, in a total concentrate with 11.1% mass recovery.
Testwork was conducted on a representative sample composited from reverse circulation (RC) chips from the Company’s Q4 2016 drilling program, which intersected mineralisation from near surface to depths of up to 151 metres. The composite sample contained 0.84% cobalt, 0.21% copper and 0.47 g/t gold.
These are first pass results and the Company expects that even better results will be achieved with optimisation. Due to the fine nature of the material, samples from RC chips are typically difficult to control during flotation and it can be expected that the results would improve for testwork carried out on core or rock samples.
Initial sighter-gravity concentration testwork indicated that a high-grade cobalt concentrate can be obtained from a small fraction of the feed mass. The results suggest that a 12.2% cobalt grade concentrate can be produced from only 1.31% of the initial mass. This has the potential to significantly reduce downstream equipment size and reagent consumption, improving both the Project’s CAPEX and OPEX.
Mineralogy has confirmed the Company’s expectations – cobalt is present as cobaltite, copper is present as chalcopyrite and the gold is predominantly associated with the sulphide minerals. The similar nature of the sulphide minerals, together with the gold association, has the potential to simplify the beneficiation process by the production of a bulk concentrate.
The testwork was managed by internationally recognised metallurgical consultants, METS Engineering (see competent person statement below) and independently carried out at ALS laboratories in Perth, Western Australia.
A micrograph of the initial flotation concentrate is shown in Figure 1, above. Cobaltite is abundant, exhibiting a highly reflective, violet-steely grey colour, and other sulphides including chalcopyrite and pyrite are also abundant, exhibiting their yellow/dark gold colour.
These results suggest excellent potential for the production of a concentrate for hydrometallurgical processing. The metallurgical testwork was conducted on RC chip samples obtained during Corazon’s Q4 2016 Drilling Program, and was carried out by ALS metallurgy in Perth, under the supervision of METS Engineering (METS).
High grade assay results were achieved at Corazon’s maiden reverse circulation (RC) and core drilling program at the Mt Gilmore Cobalt-Copper-Gold Project (“Project”) in north-eastern New South Wales.
The program focused on the high-grade Cobalt Ridge prospect and was highly successful. In total, 15 RC drill holes were completed at Cobalt Ridge and three RC holes at the Iron Mountain target, for 2086 metres. Core drilling included three tails (extensions on RC holes) for a total of 261.1 metres.
RC drilling assay results have validated the Company’s assessment of Cobalt Ridge as a unique, high-grade cobalt-dominant deposit with the potential to deliver valuable, discrete high-grade zones of cobalt, within broader moderate grade mineralisation.
Six of the 15 RC holes completed at Cobalt Ridge targeted the Main Cobalt Lode. An additional three holes have been extended with core drilling to intersect the main zone. Core drilling results are expected early in 2017.
The main cobalt lode has been drilled over a strike of about 200 metres, to a depth of 140 metres below surface (Figures 1 as presented in Corazon’s recent ASX announcement, 14/12/16 and Figure 2, below). The mineralisation is open to the west, where it is coincident with soil geochemical anomalism and small-scale historical workings targeting copper mineralisation.
The cobalt mineralisation is typically about 16 metres in down-hole width (~8 metres true width), with intersections up to 37 metres down-hole. Average cobalt grades for these intervals within the drilling completed by Corazon are between 0.23% and 0.65% cobalt. Multiple higher-grade zones of up to 1.48% cobalt exist, at between one and seven metres down hole widths. Best individual one metre assay from this program of RC drilling is 2.79% cobalt.
Significant assay results are presented in Table 1, with additional details pertaining to drilling and assaying available in Table 2 as presented in Corazon’s recent ASX announcement (14/12/16).
Cobalt Ridge – Potential Upside
Geological interpretation of the drill core and RC assay results has resulted in a fuller understanding of the mineralisation at Cobalt Ridge. As evidenced in the diamond core (Figure 3), the mineralised system displays intense pervasive alteration and sulphide filled tourmaline brecciation indicative of a larger cobalt-copper-gold system. This alteration is observed on surface at Cobalt Ridge and other prospects within the greater Mt Gilmore region.
Three priority target areas have been defined at Cobalt Ridge. None of these targets have been tested with modern exploration and it is proposed that surface geochemistry and geophysics will provide a good first-pass test.
Cobalt Ridge West – The best result from drilling by Corazon at Cobalt Ridge is the western-most hole, MGRC002. This mineralisation plunges to the west-northwest, coincident with the intersection of structures and lithologies. Additional (undrilled) structures have been identified at surface, which have the potential to generate high-grade mineralisation.
The target is supported by anomalous soil geochemistry (Figure 2, above) and abundant sub-cropping quartz-tourmaline-limonite breccia (Cobalt Ridge host rock).
Flintoff’s – This target sits immediately to the north of Cobalt Ridge and is centred on late 1800’s copper workings. These workings exhibit the same trend and host material as at Cobalt Ridge, but are substantially larger.
The edge of the Cobalt Ridge soil sampling survey just touches on this trend, returning strong anomalism (Figure 2, above).
Cobalt Ridge East – The target is situated at the intersection of the Cobalt Ridge and Flintoff’s trends, under the cover of thin sediments.
The Cobalt Ridge Prospect
The high-grade nature of this cobalt mineralisation is published in historical records from shallow mining (maximum shaft depth 36.5 metres), reporting a maximum of 14.7% cobalt (Co), 14.9% copper (Cu) and up to 1.7 oz/ ton gold (Au). The richer mineralisation seemingly occurs in small lenses or pods within a broader zone of lower-grade mineralisation.
Modern exploration within the Project commenced in the 1980’s; PanContinental completed ground IP and magnetic geophysical surveys, gridded soil geochemistry for Cu, Au and Co, 25 trenches (1518.5 metres) and 17 RC drill holes (for 1020.82 metres).
Between 2006 and 2008, Central West Gold N.L. drilled 25 holes for 2880 metres, including 21 holes for 2604 metres at Cobalt Ridge. This work defined multiple parallel sub-vertical Co-Cu-Au sulphide lodes over a strike of 300 metres and width of between 50 metres and 120 metres. Maximum individual one (1) metre drill results include 3.38% Co, 3.18% Co and 4.92 g/t Au.
The Cobalt Ridge Prospect represents an advanced cobalt play with shallowly drilled Co-Cu-Au lodes that remain open along strike and at depth.
Numerous undrilled regional cobalt prospects exist, including several defined by soil geochemistry and geophysics close to Cobalt Ridge. This style of mineralisation (Co-Cu-Au sulphides) is typically responsive to geophysics, with the Cobalt Ridge mineralisation being traced for at least an additional 100m to 200m under cover outside of existing drilling.