GR Silver Mining Reports Initial High-Grade Results from Plomosas Mine Sampling Program

Cision Canada

08-07-2025

VANCOUVER, BC, July 8, 2025 /CNW/ - GR Silver Mining Ltd. (" GR Silver Mining" or the " Company") (TSXV: GRSL) (OTCQB: GRSLF) (FRANKFURT: GPE) – is pleased to report initial results of Phase I of the new underground sampling program (the "Program") at the Plomosas Mine, Sinaloa, Mexico. The Program was designed around the following objectives:
To model the recently mapped high-grade silver zones in the interior of the historic Plomosas Mine, post completion of the March 2023 NI 43-101 mineral resource estimate ("MRE");
To collect metallurgical test work samples essential to define key parameters for implementation of a Bulk Sampling Test Mining Program (" BSTM") at the Plomosas Mine (Table 1); and
To enhance the existing database of underground samples for improved reconciliation between the MRE and areas identified for a BSTM.
Sampling Highlights
Initial highlights of the Phase I Plomosas Mine underground sampling program include:
Chip Mine Face Sample – Level 883 - 2,423 g/t Ag Eq*, consisting of 675 g/t Ag, 46.9% Pb, 4.5% Zn and 0.54 g/t Au (Polymetallic Hydrothermal Breccia – Massive Sulphide)
Channel Sample – Level 833 – 0.8 m @ 2,019 g/t Ag Eq, consisting of 137 g/t Ag, 5.74 g/t Au, 16.7% Pb, and 18.2% Zn (Polymetallic Hydrothermal Breccia – Massive Sulphide)
Channel Sample – Level 950 – 0.6 m @ 3,993 g/t Ag Eq, 310 g/t Ag, 15.20 g/t Au, 26.2% Pb and 10.2% Zn (Polymetallic Hydrothermal Breccia – Massive Sulphide)
GR Silver Mining's President and CEO, Marcio Fonseca, commented "The success of our new geological model at the Plomosas Mine, completed during the last 6 months, combined with detailed underground sampling, will be fundamental for the future development of engineering parameters to assess implementation of a Bulk Sampling Test Mining program in the underground mine. The current site has initial infrastructure and key permits in place, which can assist in any future mine and processing plant developments at the historic Plomosas Mine."
The Program will consist of two phases over the next four months, whereby Phase I assesses metallurgical data collected to support engineering studies as part of the BSTM, and Phase II will complete a much larger dataset to help refine basic mining engineering and planning. Both phases of the Program will support a decision to potentially implement a BSTM at the Plomosas Mine before year-end.
The Program leverages existing permits to operate at the Plomosas Mine, providing full access to the 7.4 km of underground development. Access to multiple areas for sampling, as shown in Figure 1, has enabled a better identification of unmined regions with high-grade, continuous silver, gold, and base metal mineralization at various levels of the underground mine. Assay results from 21 samples collected at the chosen sites (Table 1) have returned high-grade results, with values of up to 3,993 g/t Ag Eq. Multiple high-grade results indicate potential areas to advance Phase II, targeting the collection of additional metallurgical data and progress towards the implementation of a BSTM in the Plomosas Mine.
Table 1 - Phase I Underground Sampling Assay Results, Plomosas Mine
Sample
Sample ID
Underground Level
Sample
Ag Eq*
Ag
Au
Pb
Zn
Cu
Rocktype
Type
Length(m)
g/t
g/t
g/t
%
%
%
80458
815
877
127
2.07
1.0
2.7
2.9
Stockwork - Veins
80489
825
211
63
0.04
1.6
1.9
0.1
Polymetallic Veins
80494
862
910
90
0.99
11.5
8.5
0.1
Polymetallic Hydrothermal Breccia
80468
883
2,423
675
0.54
46.9
4.5
0.1
Polymetallic Hydrothermal Breccia
Chip
80478
975
370
308
0.06
0.4
0.7
0.1
Polymetallic Hydrothermal Breccia
Mine Face
80460
975
365
297
0.09
0.4
0.7
0.1
Polymetallic Veins
Sample
80491
975
805
50
0.69
12.4
5.9
0.4
Polymetallic Veins
80474
1000
822
71
1.13
13.4
4.1
0.3
Stockwork - Veins
80466
1000
587
36
0.48
2.1
6.9
1.1
Polymetallic Hydrothermal Breccia
80479
1000
170
51
0.02
1.8
1.1
0.1
Polymetallic Hydrothermal Breccia - Massive Sulphide
80472
1000
1,000
174
1.52
10.5
7.7
0.3
Stockwork - Veins
80498
833
0.8
2,019
137
5.74
16.7
18.2
0.5
Polymetallic Hydrothermal Breccia - Massive Sulphide
Channel
80499
833
1
909
71
2.32
6.7
8.8
0.3
Polymetallic Hydrothermal Breccia - Massive Sulphide
Mine Face
80500
833
0.75
386
34
0.09
8.1
1.9
0.0
Polymetallic Hydrothermal Breccia
Sample
80503
862
1.2
1,870
96
0.54
29.8
16.8
0.6
Polymetallic Veins
80504
950
0.8
1,192
28
0.18
29.5
5.0
0.0
Polymetallic Veins
80505
950
0.6
15
8
0.01
0.0
0.1
0.0
Polymetallic Hydrothermal Breccia
80507
950
0.9
64
11
0.16
0.1
0.6
0.1
Polymetallic Veins
80508
950
0.6
3,993
310
15.20
26.2
10.2
7.2
Polymetallic Hydrothermal Breccia - Massive Sulphide
80509
1000
1
421
68
0.55
2.5
5.1
0.1
Polymetallic Hydrothermal Breccia
80512
1000
1
899
864
0.07
0.1
0.2
0.1
Stockwork - Veins
Note:
Numbers may be rounded. Results are uncut and undiluted. True width not estimated as the Company does not have sufficient data from the new mineralized zones to determine the true widths of the intervals with any confidence.
* Ag Eq calculations using US$20.00/oz Ag, US$1,600/oz Au, US$0.90/lb Pb, US$1.10/lb Zn and US$3.00/lb Cu, with metallurgical recoveries of Ag – 74%, Au – 86%, Pb – 69%, Zn – 75% and Cu – 80%. Ag Eq = ((Ag grade x Ag Price x Ag recovery) + (Au grade x Au price x Au recovery) + (Pb grade x Pb price x Pb recovery) + (Zn grade x Zn price x Zn recovery) + (Cu grade x Cu price x Cu recovery)/(Ag price x Ag recovery)
The areas selected for Phases I and II of the Program consist of material where mineralization is continuous, with evidence of silver, gold and base metal mineralization at concentrations attractive for a potential BSTM in early 2026. The BSTM will also require the construction of a demonstration processing plant on site, with details to be defined after the completion of Phase II and associated engineering studies.
The Company plans to continue investigating opportunities at the Plomosas Mine, based on recent success, targeting the higher-grade silver zones in the MRE, which may support the implementation of a BSTM.
Note: Purple shapes are potential stopes blocks for BSTM. Pale grey represents existing underground developments of varying sizes, ramps and historical stopes.
About the Plomosas Project
The Plomosas Project, including the recent high-grade silver discovery in the San Marcial SE Area, is progressing in 2025 as an emerging high-grade silver district located in southern Sinaloa, Mexico. The Plomosas Project, covering 43,187 ha, benefits from mine infrastructure, road access and existing permits associated with past-producing historical mining sites. The district contains intermediate to low-sulfidation epithermal silver and gold mineralization, hosted in hydrothermal breccias and veins. Recent success in exploration and drilling has delineated wide, high-grade, shallow hydrothermal breccias in the San Marcial Area, including the SE Area discovery, where step-out drilling is progressing in 2025, aiming for continuous resource growth. At the historical Plomosas Mine, where a subsidiary of Grupo Mexico operated the underground mine from 1985 to 2000, exploratory and metallurgical programs are being conducted to support future decisions regarding the implementation of a BSTM.
QA/QC Procedures
The Company has implemented QA/QC procedures, which include the insertion of blank, duplicate, and standard samples in all sample lots sent to SGS de México, S.A. de C.V. laboratory facilities in Durango, Mexico, for sample preparation and assaying. For every sample with results above Ag >100 ppm (over limits), these samples are submitted directly by SGS de Mexico to SGS Canada Inc. at Burnaby, BC. The analytical methods include four acid Digestion and Inductively Coupled Plasma Optical Emission Spectrometry, with Lead Fusion Fire Assay and a gravimetric finish for silver above over limits. For gold assays, the analytical methods are Lead Fusion and Atomic Absorption Spectrometry, Lead Fusion Fire Assay, and gravimetric finish for gold above over limits (>10 ppm).
Qualified Person
The Qualified Person under National Instrument 43-101 Standards of Disclosure for Mineral Projects for this news release is Marcio Fonseca, P. Geo., President & CEO for GR Silver Mining, who has reviewed and approved its contents.
About GR Silver Mining Ltd.
GR Silver Mining is a Canadian-based, Mexico-focused junior mineral exploration company engaged in cost-effective silver-gold resource expansion on its 100%-owned assets, located on the eastern edge of the Rosario Mining District, in the southeast of Sinaloa State, Mexico. GR Silver Mining controls 100% of the Plomosas Project, including the former Plomosas underground mine and wide, high-grade silver mineralized zones at the San Marcial Area. Recent discoveries in the 78 km² of highly prospective, advanced-stage exploration concessions position the Company well for resource expansion at the Plomosas Project.
GR Silver Mining Ltd.
Márcio Fonseca, President & CEO
Cautionary Statement Regarding Forward-Looking Information
This press release contains "forward-looking statements" within the meaning of applicable Canadian securities legislation and information that are based on the beliefs of management and reflect the Company's current expectations. When used in this press release, the words "estimate", "project", "belief", "anticipate", "intend", "expect", "plan", "predict", "may" or "should" and the negative of these words or such variations thereon or comparable terminology are intended to identify forward-looking statements and information. Such statements and information reflect the current view of the Company. Risks and uncertainties may cause actual results to differ materially from those contemplated in those forward-looking statements and information. By their nature, forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements, or other future events, to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements.
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SOURCE GR Silver Mining Ltd.