(TheNewswire)
Highlights:
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Three samples from the mineralized zone within the Pinos Cuates underground mine were sent to the SGS Lab in Durango, Mexico for grinding, bottle roll cyanide leach and gravity tests.
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Initial grind calibration tests in a ball milling application achieved a target grind of 80% passing 270 mesh (53 micron) particle size.
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Average unoptimized reagent consumption was 0.71 kg/t NaCN and 1.62 kg/t CaO, both within expected ranges for a preliminary test.
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Initial gravity tests utilising a Knelson concentrator and Mozley table resulted in variable recoveries ranging from 29.1% to 76.38% for gold and 3.98% to 15.91% for silver.
‘We are very pleased with the results from this preliminary round of metallurgical tests , especially for gold recoveries, and considering that there were only three samples from one of the three historic mines,’ stated Robert Archer, Pinnacle’s President & CEO. ‘These tests were run using simple baseline parameters and without any optimization. The results indicate that we need to conduct mineralogical tests on the mineralization to determine the nature of the gold and silver occurrences. While it is likely that gold occurs either as free particles or in electrum, silver can occur in electrum, silver sulphides or silver sulphosalts. Once this has been established, further testing will be able to fine tune the metallurgical processes in order to increase recoveries, particularly for silver. Metallurgical testing is an iterative process, and it is expected that sampling of the other mines on the property will result in further variations. However, this is the whole point of the testing as we aim to maximize recoveries and streamline the flow sheet prior to rebuilding the plant.’
The Pinos Cuates mine is the central mine of the three historic workings on the Dos de Mayo low sulphidation epithermal vein system at El Potrero. The three metallurgical samples were taken from the raise and upper level of the mine, based upon the results of previous channel sampling. Each sample weighed approximately 25 kg. Samples were fire assayed with AAS finish for gold and silver, in duplicate, and analysed for 32 elements by 4-acid digestion and ICP finish. The latter confirmed that there are negligible amounts of copper, lead, zinc, arsenic, mercury or any other deleterious elements present. Some variation between gold analyses of the channel samples versus the metallurgical samples suggests the presence of a nugget effect, likely due to fine free gold, as silver analyses were comparable. A comparison of the two sets of analyses can be seen in the table below:
|
Channel sample |
MET sample |
Au g/t |
Ag g/t |
|
EPUG25097 |
2.91 |
108 |
|
|
EPMET25001 |
6.20 |
99 |
|
|
EPUG25136 |
13.00 |
56 |
|
|
EPMET25002 |
5.10 |
52 |
|
|
EPUG25421 |
34.60 |
228 |
|
|
EPMET25003 |
17.30 |
210 |
Prior to the bottle leaching tests, a grinding calibration was carried out for each sample using a ball mill in order to achieve the target particle size for the leaching and gravity concentration tests, which was 80% passing 270 mesh (53 microns). This information will be used in future tests on hardness and work index.
A bottle roll test was carried out for each sample, separately from the gravity test, in order to evaluate the gold and silver extraction response for each method. The bottle roll test was performed in a 2-gallon Nalgene bottle, using 1,000 g of sample, with a retention time of 72 hours. Monitoring was conducted at intervals of 12, 24, 48, and 72 hours to collect solution samples and evaluate the gold and silver extraction kinetics. Additionally, sodium cyanide and lime consumptions were determined.
Dissolution kinetics showed rapid recoveries of 79-92% for gold after only 24 hours, increasing gradually to their ultimate levels of 92.81%, 95.68% and 96.79%, averaging 95.09%, after 72 hours. Silver recoveries increased more gradually towards 41.41%, 73.53% and 49.11%, with an average of 54.68%, after 72 hours. It is considered that a longer leach time could improve the silver recoveries.
Sodium cyanide (NaCN) consumption ranged from 0.49 to 0.94 kg/t, while lime (CaO) consumption ranged from 0.93 to 2.03 kg/t, both within expected ranges for unoptimized tests.
According to the SGS report, ‘Gravity concentration using the Knelson concentrator is based on the separation of mineral particles according to their density differences, applying centrifugal force. This equipment concentrates the heavy minerals (such as free gold or high-density sulfides) into a small volume of concentrate, while the lighter material is discharged as tailings.
The concentrate obtained from the Knelson is subsequently subjected to cleaning on a Mozley table, which allows for a finer and more selective separation. This stage improves the purity of the final concentrate by removing gangue minerals and obtaining a fraction richer in valuable minerals.
For metallurgical balance purposes, the sum of the Knelson concentrate and the Mozley ‘middlings’ is necessary, since both products belong to the same gravity concentration stream and contain a significant portion of the recovered metallic values. Combining these products provides a more accurate representation of the total recovery attributable to the gravity circuit, preventing underestimation of the metallic content in the overall balance.’
Approximately 20 kg of each sample with a particle size of 53 microns was used for the gravity tests. Gold recoveries were somewhat variable, yielding 29.10%, 33.02% and 76.38%, whereas silver was a little more consistent, albeit lower, with recoveries of 3.98%, 7.77% and 15.31%. As gold is heavier than silver, it is normal for gold to yield higher recoveries in a gravity circuit. The particularly high gold recoveries of 76.38% in one sample is likely due to the presence of a higher percentage of free gold. It is worth noting that this sample also had the highest head assay of 17.2 g/t Au and the highest recovery from leaching of 96.79%.
In subsequent metallurgical work, gravity and leaching tests will likely be conducted in series, with the high-grade gravity concentrate being removed and the tails being leached. While it is normal for higher grade material to yield higher recoveries, it is also considered that a finer grind and extended leach times may improve recoveries at the lower end. These along with other optimized process details will be addressed in the next testing stage.
Qualified Person
Mr. David Salari, P.Eng., a Director of Pinnacle and a Qualified Person as defined by National Instrument 43-101, has reviewed and approved this news release.
Mr. Jorge Ortega, P. Geo, a Qualified Person as defined by National Instrument 43-101, and the author of the NI 43-101 Technical Report for the Potrero Project, has also reviewed and approved this news release.
About the Potrero Property
El Potrero is located in the prolific Sierra Madre Occidental of western Mexico and lies within 35 kilometres of four operating mines, including the 4,000 tonnes per day (tpd) Ciénega Mine (Fresnillo), the 1,000 tpd Tahuehueto Mine (Luca Mining) and the 250 tpd Topia Mine (Guanajuato Silver).
High-grade gold-silver mineralization occurs in a low sulphidation epithermal breccia vein system hosted within andesites of the Lower Volcanic Series and has three historic mines along a 500 metre strike length. The property has been in private hands for almost 40 years and has never been systematically explored by modern methods, leaving significant exploration potential.
A previously operational 100 tpd plant on site can be refurbished / rebuilt and historic underground mine workings rehabilitated at relatively low cost in order to achieve near-term production once permits are in place. The property is road accessible with a power line within three kilometres. Surface rights covering the plant and mine area are privately owned (no community issues).
Pinnacle will earn an initial 50% interest immediately upon commencing production. The goal would then be to generate sufficient cash flow with which to further develop the project and increase the Company’s ownership to 100% subject to a 2% NSR. If successful, this approach would be less dilutive for shareholders than relying on the equity markets to finance the growth of the Company.
About Pinnacle Silver and Gold Corp.
Pinnacle is focused on the development of precious metals projects in the Americas. The high-grade Potrero gold-silver project in Mexico’s Sierra Madre Belt hosts an underexplored low-sulphidation epithermal vein system and provides the potential for near-term production . In the prolific Red Lake District of northwestern Ontario, the Company owns a 100% interest in the past-producing, high-grade Argosy Gold Mine and the adjacent North Birch Project with an eight-kilometre-long target horizon . With a seasoned, highly successful management team and quality projects, Pinnacle Silver and Gold is committed to building long -term , sustainable value for shareholders.
Signed: ‘Robert A. Archer’
President & CEO
For further information contact :
Email: info@pinnaclesilverandgold.com
Tel.: +1 (877) 271-5886 ext. 110
Website: www.pinnaclesilverandgold.com
Neither the TSX Venture Exchange nor the Investment Industry Regulatory Organization of Canada accepts responsibility for the adequacy or accuracy of this release .
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