New Pacific Reports Positive Preliminary Metallurgical Test Results from Carangas with 98% Gold Recovery from Cyanide Leach
VANCOUVER, BC, Nov. 21, 2022 /CNW/ - New Pacific Metals Corp. ("New Pacific" or the "Company") (TSX: NUAG) (NYSE American: NEWP), together with its local Bolivian partner, are pleased to report the preliminary metallurgical testwork results of the five variability samples from its Carangas Silver-Gold Project in Oruro Department, Bolivia (the "Carangas Project" or the "Project"). This ongoing metallurgical testwork program consists of scoping-level cyanide leach and flotation testing and is carried out by Bureau Veritas's Metallurgical Division in Richmond, British Columbia, Canada.
Mineralized materials sampled from rejects of selected Carangas drill cores with assays were composited to five samples based on the type of mineralization and degree of oxidization. Host rock sample is altered volcanoclastic rocks of dacitic-rhyolitic composition.
Cyanide leach tests for the fresh gold samples for the sample with less than 1% sulfur content have achieved 98.8% gold recovery and the second gold sample with approximately 3% sulfur content achieved 98.5% gold recovery.
The near surface, overlying oxidized, oxidized to semi-oxidized, and fresh silver-lead-zinc samples were tested with cyanide leaching and flotation. The cyanide leach tests achieved silver recoveries of 84.1%, 85% and 74.3%, respectively. Whole ore flotation tests achieved silver recoveries of 72-77%, 90-94% and 99%, respectively. Flotation tests for oxidized to semi-oxidized samples also achieved zinc recoveries of 93-95%. Furthermore, 98-99% lead and 96-97% zinc flotation recoveries were achieved for the fresh silver-lead-zinc sample.
These preliminary test results clearly demonstrate that high recovery rates can be expected for gold using cyanide leaching and for silver, lead, and zinc through conventional cyanide leaching and flotation for silver-lead-zinc mineralized materials. The results of testwork are summarized below in Table 1.
Table 1 Summary of scoping level metallurgy tests of Carangas Project
Whole Ore Cyanide Leach |
|||
Sample # |
Mineralization |
Degree of |
Recovery |
1 |
Silver-Lead |
Oxidized |
84.1% silver recovery |
2 |
Silver-Lead-Zinc |
Oxidized to Semi- |
85.0% silver recovery |
3 |
Silver-Lead-Zinc |
Fresh |
74.3% silver recovery |
4 |
Gold |
Fresh (sulfur<1%) |
98.8% gold recovery |
5 |
Gold |
Fresh (sulfur ~3%) |
98.5% gold recovery |
Rougher Flotation |
|||
Sample # |
Mineralization |
Degree of |
Recovery |
1 |
Silver-Lead |
Oxidized |
72 -77% silver recovery into silver/lead concentrate |
2 |
Silver-Lead-Zinc |
Oxidized to Semi- |
90-94% silver recovery and 93-95% zinc recovery into |
3 |
Silver-Lead-Zinc |
Fresh |
99% silver recovery, 98-99% lead recovery and 96-97% zinc |
Sample 1
Sample 1 was an oxidized composite silver-lead sample consisting of drill core rejects from shallow depth (25-66 m) with head grades of 183 g/t silver and 1.20% lead. Zinc content was negligible. The majority of the lead was present in an oxidized form.
Initial whole ore cyanide leach testing showed that silver dissolved rapidly in cyanide solution with 84.1% silver recovery. Further cyanide leach tests along with gravity concentration will be carried out to improve silver recovery.
Early flotation testing indicated that silver recovery during rougher flotation was modest in the 72-77% range, and lead recovery was very poor. Further improvement work is in progress.
Sample 2
Sample 2 was an oxidized to semi-oxidized composite silver-lead-zinc sample consisting of core rejects from shallow depth (9-46 m) with head grades of 106 g/t silver, 0.86% lead and 0.47% zinc. A portion of the lead was present in an oxidized form.
Silver in this sample also dissolved rapidly in cyanide solution, and silver recovery was 85.0% based on a single cyanide leach test. Silver recovery is expected to improve further with additional cyanide leach testing.
Sequential selective flotation was applied to Sample 2 to produce a silver/lead concentrate and a zinc concentrate. Initial flotation testing demonstrated promising recoveries for silver (90-94%) and for zinc (93-95%) into the combined silver/lead and zinc rougher concentrates. Lead recovery was relatively poor due to partially oxidized lead minerals. Based on what has been learned from Sample 1, lead recovery of Sample 2 is expected to increase considerably when the same approaches are applied.
Sample 3
Sample 3 was a fresh composite silver-lead-zinc sample consisting of core rejects from 110-172 m depths with head grades of 151 g/t silver, 0.85% lead and 1.28% zinc. Oxidation has not occurred in this sample.
Silver in Sample 3 dissolved very slowly in cyanide solution. After 72 hours, silver dissolution was still incomplete. Silver recovery was only 74.3% based on a single cyanide leach test. A number of options are available to increase silver recovery and will be explored in future testwork.
As with Sample 2, sequential selective flotation was applied to Sample 3 to produce separate silver/lead and zinc concentrates. Initial flotation testing showed excellent flotation performance for silver, lead and zinc. When silver/lead concentrate and zinc concentrate are combined, total recoveries were 99% for silver, 98-99% for lead and 96-97% for zinc.
Sample 4
Sample 4 was a fresh composite gold sample consisting of core rejects with low sulfur content from 425-754 m depths and a head grade of 2.5 g/t gold and 0.62% sulfur. Contents of silver, lead and zinc were very low. Preliminary cyanide leach testing demonstrated exceptionally high gold recoveries in a range of 98.2-99.2%. Gold recovery was very robust and dropped only by 1.0% after grind size was coarsened from 80% passing 50 µm to 80% passing 150 µm, and cyanide concentration was reduced from 1.0 g/L NaCN to 0.50 g/L NaCN and oxygen sparging was replaced with air sparging. Sample 4 did not show any preg-robbing issue.
Sample 5
Sample 5 was a fresh composite gold sample consisting of core rejects with high sulfur content from 430-746 m depths and a head grade of 3.88 g/t gold and 3.07% sulfur. Contents of silver, lead and zinc were also insignificant. As with Sample 4, exceptionally high gold recoveries (97.2-99.0%) were achieved from initial cyanide leach tests. Gold recovery dropped only by 1.8% after grind size was coarsened from 80% passing 50 µm to 80% passing 150 µm, cyanide concentration was reduced from 1.0 g/L NaCN to 0.50 g/L NaCN and oxygen sparging was replaced with air sparging. Sample 5 also did not show any preg-robbing issue.
Based on the preliminary metallurgical test results, the following recommendations can be made with respect to the selection of flowsheet for the future process plan:
For gold materials represented by Sample 4 and Sample 5, a simple process based on cyanide leach and carbon-in-pulp (CIP) can potentially achieve an average of 98.6% gold recovery. A gravity concentration may be included to reduce gold lockup in the circuit. Gold dore will be the final product.
For silver-lead-zinc materials represented by Sample 2 and Sample 3, separate silver/lead concentrate and zinc concentrate will be produced by sequential selective flotation. The silver/lead concentrate may further be treated by cyanide leach to enable silver dore production at the mine site. The residue after cyanide leach can still be sold as silver/lead concentrate, although with significantly lower silver content.
For silver-lead-zinc materials represented by Sample 1, if lead can be effectively concentrated via flotation, the silver/lead concentrate will be produced first via bulk flotation. Gravity concentration may be included to increase silver and lead recoveries. The resultant silver/lead concentrate may also be treated by cyanide leach to enable silver dore production at the mine site. The residue from cyanide leach will be sold as silver/lead concentrate. If the residue from cyanide leach cannot be sold as silver/lead concentrate, a fallback option for the materials similar to Sample 1 is the whole ore cyanide leach for silver dore production.
This metallurgy test program was designed and supervised by Dr. Jinxing Ji who is an internationally recognized metallurgist with more than 25 years experience in working for senior Canadian mining companies related to gold, silver, copper, zinc and lead recovery, including mineral/metallurgical research and test work, development of process flowsheet and process design criteria, scoping study, pre-feasibility study, feasibility study, engineering design, plant commissioning and plant operational support/optimization for projects/mines in Turkey, Greece, Canada, China, Romania, Brazil and Papua New Guinea. Dr. Ji was the Director, of Metallurgical Services for Eldorado Gold Corp. for 15 years and the Consulting/Research Metallurgist for Placer Dome Inc. for 10 years.
The scientific and technical information contained in this news release has been reviewed and approved by Alex Zhang, P. Geo., Vice President of Exploration, who is a Qualified Person for the purposes of National Instrument 43-101 — Standards of Disclosure for Mineral Projects ("NI 43-101"). The Qualified Person has verified the information disclosed herein, including the sampling, preparation, security and analytical procedures underlying such information, and is not aware of any significant risks and uncertainties that could be expected to affect the reliability or confidence in the information discussed herein.
New Pacific is a Canadian exploration and development company with precious metal projects in Bolivia. The Company's flagship Project, the Silver Sand Silver Project, is expected to deliver a new Mineral Resource Estimate Update and a PEA by the end of 2022. The recently discovered Carangas Silver-Gold Project is undergoing a 40,000 m drill program. The third project, the Silverstrike Silver-Gold Project, commenced a 6,000 m discovery drill program in June 2022 and a near surface broad gold zone was discovered its first drill hole.
For further information, please contact:
New Pacific Metals Corp.
Phone: (604) 633-1368
U.S. & Canada toll-free: 1-877-631-0593
E-mail: [email protected]
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SOURCE New Pacific Metals Corp.
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