Altus Strategies: Excellent gold recoveries at Diba Project, Western Mali

28th October 2020

Altus Strategies Plc (AIM: ALS, TSX-V: ALTS, OTCQX: ALTUF) (”Altus” or the ”Company”) announces excellent results from metallurgical testwork on oxide and sulphide samples from the Company’s 100 % owned Diba gold project (“Diba” or the “Project”) in western Mali (“Mali”). The work was undertaken to test the amenability of Diba ores to carbon-in-leach (“CIL”) and heap leach processing.

Highlights:

  • Excellent gold recoveries from oxide and sulphide samples from Diba gold project in Mali:
    • 98.3 % recovery at moderate (75 μm) grind size on oxide sample for CIL scenario
    • 86.8 % recovery at moderate (75 μm) grind size of sulphide samples for CIL scenario
    • 95.8 % recovery at coarse (6.3 mm) crush size on oxide sample for heap leach scenario
  • Expectation for a significant upgrade to existing Preliminary Economic Assessment (“PEA”)
  • Existing PEA which applied a gold price of US$1,500/oz and a 10 % discount rate:
    • Generated a robust US$81M (post-tax) net present value (“NPV”)
    • Modelled 80 % gold recovery for oxide heap leaching, compared to 95.8 % reported
    • Did not envisage a CIL processing route, thereby excluded all sulphide ounces
  • Significant resource growth and discovery potential considered to exist at Diba:
    • Current Mineral Resource Estimate (“MRE”) remains open along strike and down dip
    • Seven further prospects within 7 km of MRE have yet to be systematically drill tested
    • A resource expansion and target definition drill programme is now being planned

Steven Poulton, Chief Executive of Altus, commented:

“The results of the metallurgical testwork on both oxide and sulphide material from Diba are simply excellent. Heap leach amenability shows 95.8 % gold recovery at a coarse crush size. This recovery is significantly higher than the 80 % modelled in the current PEA which we reported on in July. More significantly, the testwork on fresh (sulphide) samples shows that CIL processing will likely be very effective, with 86.8 % gold recovery at attractive grind sizes.

“Diba already boasts a robust US$81M post-tax NPV for the oxide ounces alone. The significantly enhanced recoveries and addition of the sulphide resource, should add considerable economic value to the Project. We have commissioned an updated independent PEA and look forward to reporting on the results in due course.

“Aside from the existing resource area, Altus has defined seven priority prospects at Diba, none of which have ever been systematically drill tested. These prospects are all located within 7 km of the current mineral resource, which itself is only 13 km from the multi-million ounce Sadiola gold mine. Altus is currently planning a drill programme for Diba and we look forward to providing an update on this in due course.”

Preliminary Economic Assessment to be updated

The Company has engaged Mining Plus UK Ltd to update the existing Diba PEA to incorporate the higher oxide recoveries reported in this release (95.8 % compared to 80 % used in the existing PEA). Importantly, the PEA will be broadened to model CIL processing to incorporate the current sulphide MRE of 33,600 ounces at 1.12 g/t Au Indicated and 153,300 ounces at 1.05 g/t Au Inferred as set out in Table 2. Incorporating the oxide and sulphide resource and using the higher processing recoveries is expected to have a materially positive impact on the current US$81m (post-tax) NPV10 as calculated under the existing PEA.

Metallurgical Testwork Programme

Grinding Solutions Limited of Truro (UK) was commissioned by the Company to investigate the heap leach and CIL amenability for the oxide and sulphide domains of the Diba gold deposit. A total of 128.5 kg of material of weathered (oxide) and deeper ‘fresh’ (sulphide) ores selected from various locations within the MRE were tested. Three samples from the oxide zone (72.0 kg) and four samples from the sulphide zone (56.5 kg) were composited to form a master sample for each domain, with a head grade of 3.74 g/t and 1.02 g/t respectively. The results of the testwork are summarised in Table 1 below.

Results of bottle roll testing on oxide samples

Coarse ore bottle roll testing on the oxide sample has shown that excellent gold extractions of up to 95.8 % can be achieved at crush sizes down to 6.3 mm, high extractions were also observed for crush size up to 16 mm where gold extraction of 94.5 % was observed. Final extractions are achieved after a leach period of approximately 240 hours.

Results of fine ore leach tests on sulphide samples

Whole fine ore leach tests on the sulphide sample reached 86.77 % at a grind size of 75 μm. Cyanide consumption for the tests was low, ranging between 0.02 kg/t and 0.18 kg/t NaCN. Lime consumption ranged between 0.51 kg/t and 0.71 kg/t CaO.

Results of fine ore leach tests on oxide samples

Whole fine ore leach tests on the oxide sample reached 98.3 % at a grind size of 75 μm. Cyanide consumption for the tests was low, ranging between 0.03 kg/t and 0.18 kg/t NaCN. Lime consumption ranged between 0.98 kg/t and 1.27 kg/t CaO. Leach curves were marginally downward trending towards the end of the test. Leaching was largely complete after 6 hours with the feed grade and tails grade recovery results matching well with the solution-based calculations ranging from 96.66 % to 98.36 %.

Results of flotation tests

Flotation testing was used to investigate the production of a low mass pull pre-concentrate to minimise eventual plant operating costs and capital costs. The testwork generated a flotation concentrate between 62.8 % and 67.3 % to mass pulls of between 3.9 % and 5.9 %. The results indicated that further gold recovery could be achieved by extending the flotation time and optimising reagent conditions.

Results of gravity tests

Gravity testing on oxide and sulphide samples was completed using a Falcon L40 concentrator operating at 200 G. Mass pulls to the concentrate were high at 11.6 % for the sulphide sample and 8.0 % for the oxide sample. However, gold recoveries to these concentrates were relatively low at 34.8 % and 30.7 % for the sulphide and oxide samples respectively.

The following figures have been prepared and relate to the disclosures in this announcement and are visible in the version of this announcement on the Company’s website (www.altus-strategies.com) or in PDF format by following this link: https://altus-strategies.com/site/assets/files/4929/altus_nr_-_diba_met_28_oct_2020.pdf

  • Location of the Diba project in western Mali is shown in Figure 1.
  • Location of Diba MRE area and additional targets is shown in Figure 2.

Notes on Testwork Procedures

Cyanidation Testing (Oxide Coarse Ore Bottle Roll Tests)

  • Coarse ore bottle roll tests were completed on an oxide composite.
  • Crush sizes of 20 mm, 16 mm, 12.5 mm, 6.3 mm utilising a 28 day maximum leach period and a 1 min/hour rolling period.

Cyanidation Testing (Sulphide and Oxide Fine Ore Bottle Roll Tests)

  • Fine ore cyanide leach tests were completed on sulphide and oxide composites.
  • Tests were completed using 40 % solids with grind sizes of 250 μm, 180 μm, 125 μm, 75 μm, 45 μm over two day leach period with continuous bottle rolling.

Flotation Testing

  • A series of flotation tests were completed on samples of the sulphide composite to investigate the recovery of gold to a bulk sulphide concentrate. Grind sizes of 250 μm, 180 μm, 125 μm, 90 μm, 75 μm were adopted with concentrates extracted after 1, 3, 6, 10, and 15 minutes.

Gravity test work

  • A 1 kg sample of each of the sulphide and oxide samples were submitted to a 1 kg single pass test using Falcon L40 multi gravity concentrate. A grind size P80 75 μm was used with Falcon concentrates cleaned with a Mozley table.

Diba Project: Location

The 81 km2 Diba (Korali Sud licence) project is located in the Kayes region of western Mali, approximately 450 km northwest of the capital city of Bamako. The Project sits 5 km west of the Company’s Lakanfla gold project, which is under joint venture with ASX listed Marvel Gold Limited and approximately 13 km south of the multi-million ounce Sadiola gold mine and 35 km south of the multi-million ounce Yatela former gold mine. Diba is bounded by the Sadiola permit on its northern and eastern boundaries. Mineralisation hosted on these properties is not necessarily indicative of mineralisation hosted at Diba.

Diba Project: Geology and Mineralisation

Mineralisation at the Diba project is sediment-hosted within a series of stacked lenses, typically between 20m and 40m thick. The lenses are shallow-dipping at approximately 30 degrees angled to the east/east-southeast. The deposit is considered to be controlled by a number of northwest and northeast orientated structures, with gold occurring as fine-grained disseminations in localised high-grade calcite-quartz veinlets. Alteration at Diba is typically albite-hematite+/-pyrite, although pyrite content is generally very low (<1 %). The weathering profile at the property is estimated to be up to 70m vertical depth, resulting in extensive oxidation from surface. The oxide gold mineralisation at Diba is predominantly found in saprolite within 50m of surface and across a compact 700m x 700m area.

Diba Mineral Resource Estimate

The Diba project hosts an MRE of 217,000 ounces at 1.39 g/t Au (Indicated) and 187,000 ounces at 1.06 g/t Au (inferred) in both oxide and fresh domains as set out in Table 2. The MRE was previously reported by the Company on 06 July 2020 (see Altus’ news release titled “Significant Gold Resource at Diba Project, Western Mali”). The MRE remains open downdip and along strike.

Qualified Persons

Julian Aldridge, CGeol (FGS) Principal Geology Consultant, Mining Plus UK Ltd is responsible for the Mineral Resources contained in this press release and is a Qualified Person under the terms of NI 43-101.

Phil Hingston, MIMMM, Technical Manager, Grinding Solutions Ltd is responsible for the metallurgical testwork reported in this press release, and is a Qualified Person under the terms of NI 43-101.

The technical disclosure in this regulatory announcement has been approved by Steven Poulton, Chief Executive of Altus. A graduate of the University of Southampton in Geology (Hons), he also holds a Master’s degree from the Camborne School of Mines (Exeter University) in Mining Geology. He is a Fellow of the Institute of Materials, Minerals and Mining and has over 20 years of experience in mineral exploration and is a Qualified Person under the AIM rules and National Instrument 43-101 “Standards of Disclosure of Mineral Projects of the Canadian Securities Administrators”.

For further information you are invited to visit the Company’s website www.altus-strategies.com or contact:

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