Northisle Announces Recoveries of 90% Gold and 80% Copper at Northwest Expo and accelerates 2024 Project Development Timeline
Highlights:
- Strong gold recoveries averaging 89.8% from preliminary metallurgical testing at Northwest Expo using conventional flotation followed by cyanide leaching of the flotation tails
- Attractive copper recoveries averaging 80.2% with a 24.4% copper concentrate grade from locked cycle testing
- Low SAG milling and moderate ball milling energy requirements
- High quality copper concentrates, all penalty elements within allowable limits
- Initial mineral resource estimate for Northwest Expo completion on track for Q1 2024
- Review of project opportunities incorporating Northwest Expo, Red Dog and Hushamu underway
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Figure 1: Process Flowsheet Applied to Northwest Expo Composites (Photo: Business Wire)
2024 Project Development Timeline:
Upon completion of the initial Northwest Expo mineral resource estimate during Q1 2024, the company will review opportunities to optimize the
Summary of Metallurgical Testing Procedures and Results:
The test program was developed and managed by Ausenco Engineering Canada ULC (“Ausenco”) and
Table 1 below summarizes the locked cycle flotation and leach results from tests conducted on chlorite-magnetite (“CMG”) and silica-clay-pyrite (“SCP”) composites. The average recoveries to be used in the mineral resource estimate are provided in the MRE Recoveries columns. Gold recoveries are significantly better than the Hushamu and Red Dog recoveries (see the Amended 2021 North Island Copper and Gold Project Preliminary Economic Assessment filed
Table 1: Summary of Metallurgical Tests on Northwest Expo 2023 Drill Core |
||||||||||||
Material |
Primary Grind µm P80 |
Regrind µm P80 |
Feed Grades |
Flotation Distribution |
CN Leach Extraction |
Recovery % |
Combined Au Recovery % |
MRE Recoveries |
||||
Cu % |
Au g/t |
Stream |
Cu % |
Au % |
Au % |
Cu % |
Au % |
|||||
CMG |
150 |
15 |
0.13 |
0.98 |
Con |
76.7 |
64.8 |
|
|
92.6 |
72.7 |
90.6 |
Clnr Tail |
4.5 |
13.2 |
77.8 |
10.2 |
||||||||
Ro Tail |
18.8 |
22.1 |
79.6 |
17.6 |
||||||||
150 |
19 |
0.12 |
0.87 |
Con |
68.7 |
53.8 |
|
|
88.7 |
|||
Clnr Tail |
8.1 |
20.2 |
80.1 |
16.2 |
||||||||
Ro Tail |
23.2 |
26.0 |
72.0 |
18.7 |
||||||||
SCP |
150 |
12 |
0.2 |
0.76 |
Con |
87.7 |
64.8 |
|
|
88.9 |
87.7 |
88.9 |
Clnr Tail |
4.4 |
18.6 |
60.9 |
11.4 |
||||||||
Ro Tail |
7.9 |
16.6 |
77.1 |
12.8 |
||||||||
AVG (CMG and SCP) |
0.16 |
0.84 |
|
|
|
|
|
|
80.2 |
89.8 |
Copper concentrate grades averaged 21.6% in CMG and 27.2% in SCP.
The testing procedure was carried out on half core from drill holes NW23-9, NW23-11, NW23-12, NW23-13 and NW23-14 from the Northwest Expo 2023 drill program. A listing of the drill intervals used in the test program is presented in Table 2 below.
Table 2: Northwest Expo 2023 Drill Core Intervals Used in Test Program |
||||
Alteration |
Hole ID |
Interval (m) |
Received kg |
|
From |
To |
|||
CMG |
NW23-09 |
269.7 |
305.1 |
66 |
NW23-09 |
343.3 |
370.0 |
56 |
|
NW23-11 |
255 |
285.5 |
64 |
|
NW23-12 |
360 |
384 |
43 |
|
NW23-12 |
387 |
416.7 |
66 |
|
NW23-14 |
387 |
414 |
57 |
|
SCP |
NW23-11 |
198 |
228 |
50 |
NW23-12 |
230 |
245 |
53 |
|
NW23-12 |
315 |
345 |
58 |
|
NW23-13 |
317 |
347 |
58 |
|
SCP/CMG |
NW23-13 |
266 |
299 |
69 |
NW23-13 |
224 |
245 |
45 |
Further details of the drill holes noted above, including data verification and QA/QC can be found in Northisle’s press release “Phase 2 Drilling at Northwest Expo Extends Strike of
The core was first crushed to -6 mesh and prepared into master composite and variability test charges. A series of bench scale rougher and cleaner flotation tests were then conducted on the samples (2 and 4 kg test charges) at primary grind sizes ranging from 75 to 150μm P80. Flotation reagents used included 3418A, PAX and MIBC. The pH was varied from 6.6 to 11. Rougher concentrate regrind discharge sizes varied between 12 to 19μm P80 prior to three stages of cleaner flotation.
Rougher and cleaner tails were both subsequently leached using sodium cyanide by bottle roll methods to maximize gold extraction. The copper grades were sufficiently low in both the rougher and flotation tails and did not impact leaching performance. The rougher tails were leached for 24 hours as the gold extraction appeared to complete. The cleaner tails were pre-aerated with additional oxygen for 2 hours and subsequently leached for 48 hours, although the gold extraction was likely complete significantly earlier.
Comminution tests were also performed with average Axb values of 84 and 67 for CMG and SCP samples, respectively. The average Bond ball mill work index was 16.9 kWh/t for all samples. The samples have a lower resistance to breakage in a SAG mill than values measured on Hushamu and Red Dog samples, however the ball mill work index values are slightly higher.
Figure 1 shows the process flowsheet applied in the test program.
The flotation portion of the flowsheet is very similar to that applied to Hushamu and Red Dog samples in earlier test programs.
Qualified Persons
The scientific and technical information contained in this news release has been reviewed, verified, and approved by Northisle Copper and Gold’s Vice President of
The information in this press release relating to metallurgical test work results has been reviewed and verified by Peter Mehrfert,
Data Verification and QA/QC
Data verification consisted of the Qualified Persons listed above (the “QPs”) ensuring that the samples selected came from within the area which is likely to be included in Northisle’s planned resource estimate, and that the selected samples are generally consistent with the mineralized material to be incorporated in that estimate. The QPs checked that the sampling protocol used by BaseMet was applicable for the planned testwork. In the QPs’ opinion, the testwork conducted was completed by a reputable metallurgical testing facility and used industry-standard methods. Peter Mehrfert,
About Northisle
For more information on Northisle please visit the Company’s website at www.northisle.ca.
On behalf of
Cautionary Statements regarding Forward-Looking Information
Certain information in this news release constitutes forward-looking statements under applicable securities law. Any statements that are contained in this news release that are not statements of historical fact may be deemed to be forward-looking statements. Forward-looking statements are often identified by terms such as “may”, “should”, “anticipate”, “expect”, “intend” and similar expressions. Forward-looking statements in this news release include, but are not limited to, statements relating to anticipated timing of the company’s activities, marketability of potential products from a potential future development, expectations regarding technical studies, timing of key catalysts; planned activities, including further drilling, at the
Readers are further cautioned not to place undue reliance on forward-looking statements as there can be no assurance that the plans, intentions, or expectations upon which they are placed will occur. Such information, although considered reasonable by management at the time of preparation, may prove to be incorrect and actual results may differ materially from those anticipated. Forward-looking statements contained in this news release are expressly qualified by this cautionary statement.
The forward-looking statements contained in this news release represent the expectations of management of Northisle as of the date of this news release, and, accordingly, are subject to change after such date. Northisle does not undertake any obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as expressly required by applicable securities law.
Neither the
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Chief Financial Officer
Tel: (778) 655-9582
Email: info@northisle.ca
www.northisle.ca
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