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Market Announcement
24 November 2021
CNX Mineral Resource Update
Highlights:
- Independent Mineral Resource Estimate completed for CNX gold deposit
- Local Uniform Conditioning (LUC) approach applied at CNX to report recoverable resources and assist with preparation for maiden Ore Reserve
- Practical approach for CNX-style mineralisation delivers resource including reasonable open pit dilution
- CNX mineralisation remains open at depth and along strike, highlighting the outstanding potential of this key Coolgardie gold deposit
West Australian gold explorer Focus Minerals (ASX: FML) (Focus or the Company) announces the completion of an independent Mineral Resource estimate for the CNX deposit, part of the Company's Coolgardie Gold Project. The independent Mineral Resource Estimate was completed by Cube Consulting (Cube).
CNX is a key deposit within the Coolgardie Gold Project (Coolgardie), which covers 175km2 of highly prospective tenements on the outskirts of the Coolgardie township in the Goldfields region. CNX is located immediately north-west along strike of the Three Mile Hill open-cut mine (Figure 1) and close to the Three Mile Hill processing plant (in care and maintenance).
Cube provided technical assistance and review of data leading to the October 2021 CNX Geological Mineral Resource update (refer ASX announcement dated 28 October 2021). The October resource estimate targeted all mineralisation at CNX including zones of thinner and in places thinner and lower- grade mineralisation.
As part of this work with Cube, a preliminary Local Uniform Conditions (LUC) resource estimate was completed in October as a cross-check for QAQC purposes. It was noted during this work that the LUC model performed well when compared with reported 1991 production from the CNX trial pit, which has been relatively heavily drilled. Following completion of the October Mineral Resource update by the Company, Focus decided to formally complete the CNX LUC resource estimate so it could be assessed for use with follow-up reserve estimation.
The independent LUC Mineral Resource estimate for CNX delivered by Cube reported mineable blocks that included reasonable dilution by estimating tonnage and grade of mineralisation, which can be recovered using a Selective Mining Unit (SMU). Essentially, the LUC process characterises thin and lower-grade mineralisation that can present as sub-grade in an open pit mining environment. This independently prepared resource update differs to the CNX Mineral Resource reported by Focus in
Focus Minerals Limited | |
ACN 005 470 799 | ABN 56 005 470 799 | ASX: FML | |
Level 2, 159 Adelaide Terrace, East Perth WA 6004 | PO Box 3233, East Perth WA 6892 | |
T +61 (0) 8 9215 7888 | F +61 (0) 8 9215 7889 | E info@focusminerals.com.au | W focusminerals.com.au | Page 1 of 28 |
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October because it excludes thin mineralised zones. This feature applies only to the resource model used by Focus for the CNX deposit.
The newly completed LUC Mineral Resource estimate has now been reviewed and Focus has decided to use it for the maiden CNX Ore Reserve estimation, which will be completed in coming months. The mineralisation at CNX remains open at depth and along strike and Focus is confident in CNX. Further extensional drilling work and Mineral Resource updates at CNX are planned for 2022.
CNX sub-crops over a drill-defined strike of 700m. The resource is truncated 97m north of the Great Eastern Highway centreline. The independent CNX open pit LUC Mineral Resource is reported on a dry tonnage basis using a 0.5 g/t Au cut-off to 200mRL (depth of 230m):
Classification | Tonnage | Au Grade | LUC Contained | ||||||
(Mt) | (g/t) | Au Koz | |||||||
Measured | 2.7 | 1.08 | 93,800 | ||||||
Indicated | 1.1 | 1.08 | 37,900 | ||||||
Inferred | 0.8 | 1.0 | 26,200 | ||||||
Total Mineral Resource | 4.6 | 1.06 | 157,900 | ||||||
The independent LUC Mineral Resource estimate has significantly increased tonnes of mineralisation reporting above cut-off and only resulted in a 15% reduction in Total Measured and Indicated Mineral Resources. Inferred Mineral Resources in less well-drilled parts of the CNX deposit have reduced by 50%, largely as a result of limited drilling in those areas.
Commenting on the independently compiled CNX Mineral Resource, Focus Minerals' CEO, Mr Zhaoya Wang, said:
"The headline number of this independently compiled Mineral Resource is lower than the Mineral Resource update released by Focus last month but should be seen as an intermediate resource estimation only, without diluting the potential of this important Coolgardie gold deposit.
"Focus is very comfortable with this more conservative resource estimation, which is appropriate for a growing deposit like CNX. Focus looks forward to the next phase of resource development at CNX.
"We will use this independent LUC Mineral Resource estimate to help prepare the maiden CNX Ore Reserve estimate, which will now be concluded during the March 2022 Quarter."
Market Announcement | Page 2 of 28
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CNX (Caledonia North Extended)
Emerging bulk-tonnage pit option reshaping the Coolgardie mine plan
CNX is located on the north-west extension of the Three Mile Hill open pit. The strike of the Mineral Resource being reported is 700m and reported to a vertical depth of 230m from surface. The southeast extension of the mineralisation is cut off using an exclusion zone 97m north of the Great Eastern Highway centreline. CNX is located only 1.25km north north-west of the Three Mile Hill ROM pad.
Figure 1: Coolgardie location map highlighting recent Mineral Resource updates and Mineral Resources currently
under review.
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CNX Location and Historic Production
The CNX deposit is contiguous with the Three Mile Hill open pit, which had historic production of 4.2Mt
- 2.4 g/t Au for 324Koz. CNX is located on the north-western extension of the Three Mile Hill Mineral Resource, starting on the north-western side of Great Eastern Highway.
Exploration has been conducted along strike of CNX. This drilling has confirmed the presence of the host G2 Gabbro, extending a further 800m north-east and around a fold into the Green Light target.
21CNRC015 |
19.00m @ 1.93g/t from 64m |
for (GxM 36.7) |
21CNRC023 |
20.00m @ 0.9g/t from 85m |
for (GxM 18) |
Green Light |
+400m strike |
21CNRC001 |
33.00m @ 0.89g/t from 87m |
for (GxM 29.4) |
20CNRC001 |
37.00m @ 3.49g/t from 59m |
for (GxM 129.1) |
21CNRD003 |
18.00m @ 1.6g/t from 125m |
for (GxM 28.8) |
21CNDD004 |
20.00m @ 5.2g/t from 178m |
for (GxM 104) |
21CNRD027 |
10.00m @ 7.14g/t from 185m |
for (GxM 71.4) |
Figure 2: Plan view showing the location of CNX along strike from the Three Mile Hill deposit. The 2D location of significant intersections drilled in 2020-21 exceeding 0.5g/t and including up to 3m internal dilution are shown by dots, coloured as: CNX (red dots), Gap Zone (blue dots) and Green Light (green dots). The G2 Gabbro (pink semi- transparent polygon) is the host of the majority of the CNX and Green Light mineralisation. The G2 Gabbro strikes north-west at Three Mile Hill, CNX and the Gap Zone. At the east side of Green Light, the G2 Gabbro is folded and strikes west south-west. The location of section box for Figure 3 (light blue box) is also shown. Princess Midas shallow workings and minor shafts are shown as orange stars. The larger Princess Midas shaft is marked by a red star. The October 2021 Resource reporting box is marked by the dark blue rectangle with 97m offset from the centreline of Great Eastern Highway.
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The 1991 CNX trial pit was mined as a 30m-deep and 270m-longnorth-west striking open pit. Archives indicate the following pre-mining Open Pit Mineral Resource estimate and post-mining reconciliation:
Classification | Tonnes | Au Grade | Au Contained | ||||||||
(g/t) | Oz | ||||||||||
1991 Trial Pit Mineral Resource Estimate 1 g/t cut off | 120,00 | 2.1 | 8,000 | ||||||||
1991 Trial Pit Estimated 20% dilution @ 0.3 g/t | 24,000 | 0.3 | 200 | ||||||||
1991 Trial Pit Estimated Recovered Diluted Mineral | 143,000 | 1.8 | 8,200 | ||||||||
Resource 1 g/t cut off | |||||||||||
Reconciled Trial Pit Recovered Mineral Resource at | 196,000 | 1.9 | 11,700 | ||||||||
1 g/t cut off | |||||||||||
Reconciliation % | +36.5% | +3.9% | +41.9% | ||||||||
CNX Geology and Structure Summary
Infill drilling at CNX, and in particular a significant amount of orientated HQ diamond core, has confirmed that the structural controls are identical to those at Three Mile Hill. Focus continues to use a significant amount of diamond drilling at CNX, accounting for 56% of all CNX resource and feasibility drilling since October 2020.
The main control on the bulk-style tabular mineralisation at CNX is the G2 Gabbro (Figures 2 and 3). Within the G2 Gabbro, 0.5cm to +5cm quartz-chlorite-sulphide veins form a series of stacked, shallow south-west dipping stockworks (Figure 3). Higher-grade mineralisation dips south-east within the G2 Gabbro and is characterised by sets of 5cm to 30cm-thickquartz-chlorite-sulphide veins.
Figure 3: Sectional view north-west of the interpreted cross section 20CNDD004. The sub-vertical yellow polygon shows the location of the modelled G2 Gabbro that hosts the majority of the CNX mineralisation. The labelled significant intersection was calculated using a 0.5g/t cut-off and up to 3m internal dilution. Red polygons show the location of the bulk-style CNX mineralisation. A preliminary pit design that was developed to assess the December 2020 CNX Mineral Resource update is also shown.
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