More Bonanza Grade Gold-Silver at Los Reyes as Ongoing Drilling Expands Guadalupe East and Zapote South

VANCOUVER, May 25, 2021 - Prime Mining Corp. ("Prime" or the "Company") (TSX-V: PRYM), (OTCQB: PRMNF), (Frankfurt: A2PRDW), announces additional positive results from its continuing 15,000-metre first phase drill program ("Phase 1") at its wholly owned Los Reyes gold-silver project in Sinaloa state, Mexico. The results include new drill core assays from the Guadalupe East and Zapote South deposits which are two of eight known gold-silver deposits that comprise the current mineral resource at Los Reyes. Twelve drill holes are being reported on, including seven holes from Guadalupe East, and five holes from Zapote South (see Figure 1). An additional four drill holes have also been completed at Guadalupe East, each encountering the Estaca vein, with assays pending. A seventh drill rig has been added to the project as the Company pursues completion of Phase 1 drilling prior to the upcoming rainy season.

Key Highlights:

Guadalupe East

• Drill hole 21GE-03 targeted the Estaca vein at Guadalupe East in an area with no known historic mining or previous drilling to gain more geologic and structural controls and aid in further planning of step-out drilling. Access and topography constraints required hole 21GE-03 to be drilled at a high angle to the interpreted mineralized system. The drill hole successfully intercepted the Estaca vein with a drill core length of 58.0 metres ("m"), 11.6 m estimated true width ("etw"), returning 8.12 grams per tonne ("gpt") gold ("Au") and 724.6 gpt silver ("Ag"). Contained within this intercept are three discrete mineralized zones: two upper vein breccia zones separated by 3.5 m (0.7 etw) of waste and a lower mineralized stockwork unit separated from the lower vein breccia by 4.5 m (0.9 m etw) of waste. The first vein breccia intercept was 28.0 m (5.6 m etw) of 11.95 gpt Au and 1,122.1 gpt Ag and the second vein breccia intercept was 10.0 m (2.0 m etw) at 11.17 gpt Au and 909.3 gpt Ag. The lower stockwork unit intercept was 12.0 m (2.4 m etw) at 2.00 gpt Au and 120.9 gpt Ag.
• Drill hole 21GE-03 intersected the Estaca vein approximately 125 m higher in elevation and nearly 70 m northwest of previously reported hole 21GE-01 which intersected 20.1 m at 3.25 gpt Au 380.0 gpt Ag, including 6.5 m at 6.51 gpt Au and 587.5 gpt Ag (described in our March 18, 2021 news release). These intercepts, and the historic intercepts in drill holes 12GV-02 and 12GV-03, establish that significant mineralization persists at shallower, open pit depths and the resource has expansion potential to the southeast.
• Drill holes 21GE-09 and 21GE-10 have also intersected the Estaca vein in previously undrilled areas below historic mining. Drill holes 21GE-11 and 21GE-13 intersected the Estaca vein westwards toward the boundary of the current Guadalupe East pit-constrained Inferred resource. Assays are pending for these four drill holes.
• Drill holes 21GE-05 and 21GE-07 intersected new mineralized structures adjacent to the Estaca vein. Hole 21GE-05 intercepted 1.5 m (1.4 m etw) at 10.50 gpt Au and 300.0 gpt Ag and hole 21GE-07 intersected 0.9 m (0.6 m etw) at 93.80 gpt Au and 829.0 gpt Ag. These new structures also potentially expand the current Guadalupe East pit-constrained Inferred resource.

Zapote South

• Drill hole 21ZAP-15 intercepted 8.3 m (7.4 m etw) at 4.49 gpt Au and 67.9 gpt Ag, representing a 40.0 m step-out. Hole 21ZAP-15 is the most southerly intercept drilled at Zapote South to-date. Additionally, hole 21ZAP-14 intercepted 10.4 m (7.3 m etw) grading 2.12 gpt Au and 42.3 gpt Ag. Both holes demonstrate the potential to expand current open pit resources.
• Drill hole 21ZAP-09 is an in-fill hole that intercepted 15.9 m (15.9 m etw) at 2.01 gpt Au and 35.7 gpt Ag plus another 23.4 m (23.4 m etw) at 5.56 gpt Au and 59.0 gpt Ag, including an interval with 8.6 m (8.6 m etw) at 14.09 gpt Au and 105.1 gpt Ag. Hole 21ZAP-09 provides significant missing silver information to the resource block model.

Chief Executive Officer, Daniel Kunz commented, "We are excited to have encountered more bonanza grade gold and silver mineralization in ongoing drilling at Guadalupe East that has both open pit and now underground resource potential and that remains open at depth and to the south. Drilling the bonanza grade mineralization at Guadalupe East requires solving problems caused by historic workings, access logistics and the depth of targeted mineralization from surface. We have mobilized a more powerful drill rig to help address these challenges. At Zapote South, we are also seeing anticipated gold and silver grades that extend mineralization towards Tahonitas."

A graphic accompanying this announcement is available at https://www.globenewswire.com/NewsRoom/AttachmentNg/b0f1fb2f-7f10-4a4f-8321-7b18f377be85

The Estaca Vein - Guadalupe East

The Guadalupe structure was first mined as early as 1772, with the most active period of mining taking place between 1872 - 1938. The Estaca Vein is one of three principal veins mined at Guadalupe East yet remains largely untested by drilling. Drill campaigns by prior operators established a limited understanding of the true orientation of the vein. Targeting mineralization is challenging because of topography, access constraints and voids associated with historic mining. Only three of more than a dozen drill holes completed by prior operators intersected the bonanza-style mineralization previously mined at Guadalupe East. Current 3D modelling and re-interpretation of these drill intersections indicates a steep southwest dipping vein geometry. Mineralization is typical of low sulphidation epithermal systems, comprising massive to drusy, colliform to crustified adularia bearing quartz and quartz breccias.

Table 1: Relevant Guadalupe East, San Nicolas, and Estaca Vein Intersections¹

Footnotes
¹⁾ A complete table of assay results from all secondary zones intersected utilizing a 0.2 gpt Au cut off -- see link here.
²⁾ True widths are estimated based on drill hole geology or comparisons with other on-section drill holes.
³⁾ Composite assay grades presented in summary tables are calculated using an Au grade minimum average of 0.2 gpt or 1.0 gpt as indicated in "Au Cut-off" column of Summary Tables. Maximum internal waste included in any reported composite interval is 3.0 m. The 1.0 gpt Au cut-off is used to define higher-grade "cores" within the lower-grade halo. These higher-grade cores reflect geology and are comprised of solid quartz veining with notable adularia as opposed to quartz breccia and stockwork zones.

*This intercept was modified from the normal compositing criteria used to report in the previous news releases and this current news release to account for the overall length of mineralized intercept. Two intervals of 3.5 m (213.0 m - 216.5 m) and 4.5 m (226.5 m - 231.0 m) of internal waste did not meet the minimum 3.0 m requirement and minimum assay of 0.2 gpt Au to be included as internal dilution for the broader intercept. The broader interval is reported because the estimated true width of the internal waste component is only 0.7 m and 0.9 m respectively.

Drill hole 21GE-03 targeted the Estaca vein in an area that appears to have had no historic mining and is just outside the Guadalupe East planned Inferred resource open pit shell. Hole 21GE-03 intersected the Estaca vein at a high angle entering from the footwall through to the hanging wall. It intercepted a 58.0 m (11.6 m etw) mineralized package that includes two zones of internal waste totalling 8.0 m (1.6 m etw). The drill hole intercepted two mineralized vein and vein breccia zones separated by 3.45 m (0.7m etw) of waste rock, and a lower stockwork vein system separated from the upper veins by 4.5 m (0.9 m etw) of waste. The first interval was 28.0 m (5.6 m etw) of 11.95 gpt Au and 1,122.1 gpt Ag and the second consisted of 10.0 m (2.0 m etw) at 11.17gpt Au and 909.3 gpt Ag. Significant adularia and what has been interpreted as black colored silver sulphosalt minerals were noted in the drill core where the highest silver grades were reported. Approximately 4.5 m (0.9 m etw) of waste separates the lower mineralized vein with a mineralized stockwork zone grading 2.00 gpt Au and 120.9 gpt Ag over 12.0 m (2.4 m etw). See Figures 2, 3, and 4: Guadalupe East - Plan Map, Cross Section and Long Section.

Four additional holes have been completed with assays currently pending. Holes 21GE-09 and 21GE-10 targeted the Estaca vein at a depth below the known historic workings. Holes 21GE-11 and 21GE-13 intersected the Estaca vein closer to the bottom of the current Inferred category open pit resource.

Major Drilling Group International Inc. has now mobilized a larger diamond drill rig. This rig has the capability of drilling to 800 m with NQ core and over 1000 m with BQ core and has started to target potential extensions of the Estaca vein along strike to the southeast and at depth. This rig is positioned to drill the mineralized system from the hanging wall to footwall. These are deep holes that will provide a better indication of geology and true thickness of the Estaca vein system. Follow up drilling will also target shallow areas of the resource where opportunities exist to potentially expand the open pit and access high-grade mineralization at shallower depths.

Graphics accompanying this announcement are available at
https://www.globenewswire.com/NewsRoom/AttachmentNg/7f67ca8a-3579-439e-a457-d4caa7abf202

https://www.globenewswire.com/NewsRoom/AttachmentNg/4cd67929-209e-486f-a2d3-69a0dc86f675

https://www.globenewswire.com/NewsRoom/AttachmentNg/82c1bf3c-6022-44b0-b2a7-eba5fb534c39

The San Nicolas Vein - Guadalupe East

San Nicolas, together with Estaca and San Manuel, is one of three principal veins historically mined underground at Guadalupe East and remains largely untested by drilling. Drill holes 21GE-05 and 21GE-07 have intercepted a high-grade, shallow vein breccia zone that dips to the north and is interpreted as a potential extension of the San Nicolas vein. Hole 21GE-05 intercepted 1.5 m (1.4 m etw) grading 10.50 gpt Au and 300.0 gpt Ag and hole 21GE-07 located 15.0 m down-dip from hole 21GE-05 intercepted 0.9 m (0.6 etw) grading 93.80 gpt Au and 829.0 gpt Ag. Hole 21GE-05 also encountered a lower zone of mineralization intercepting 7.8 m (3.9 m etw) grading 0.45 gpt Au and 37.5 gpt Ag. Additional shallow drilling using oriented core technology will help determine the extent and alignment of these structures.

Zapote South

Mineralization at Zapote South consists primarily of white to grey crystalline to chalcedonic quartz, quartz breccia and stockwork exploiting 45-degree southwest dipping fault structures within or along the margins of rhyolite dykes that intrude both andesitic tuffs and rhyolite. Quartz is massive-to-crustiform, locally displaying colliform to bladed replacement textures. Higher-grade intervals are marked by finely banded green adularia. Gold distribution appears to be zoned within the quartz bearing structure. The structure appears to have 1.0 to 5.0 m thick, higher-grade core, where grades exceed 4.0 gpt Au. This high-grade core is contained within a much broader 10.0 m plus thick zone of mineralization that has a gold grades of greater than 0.2 gpt. Higher-grade structures appear continuous from section to section locally.

A graphic accompanying this announcement is available at https://www.globenewswire.com/NewsRoom/AttachmentNg/3f4710ea-afc7-4a80-a7aa-ff7be65d7b2a

The optimum elevation for higher-grade mineralization at Zapote South appears to be between 710 m and 580 m elevation above sea level ("asl"). Quartz and quartz breccia zones become generally narrower and lower grade above this elevation. Immediately below the 580 m asl, the quartz bearing zones appear to broaden into wider, lower grades zones and may lack a higher-grade center, before thinning at depth. Silver appears to have an uneven distribution throughout the mineralized interval but, in general, highest-grade silver is associated with higher-grade gold.

Table 2 shows new drill hole results from Zapote South, where the current program targets both in-fill drilling to provide additional geological and silver grade data and resource expansion drilling. 21ZAP-13, 21ZAP-14, and 21ZAP-15 were step-out holes to the south to test for extensions of the main structure. Drill hole 21ZAP-15 intercepted 4.49 gpt Au and 67.9 gpt Ag over 8.3 m (7.4 m etw) representing a 40.0 m step-out. This represents the most southerly intersection to date at Zapote South. Hole 21ZAP-14 intercepted 10.4 m (7.3 m etw) grading 2.12 gpt Au and 42.3 gpt Ag. Both holes indicate important open pit expansion potential at Zapote South and were within the optimum higher-grade elevation. See Figure 5: Zapote South Drill Hole Location Map.

Drilling has now moved to the Tahonitas road system to better target extensions of the Zapote South mineralized system.

Table 2: Relevant Zapote South Main Structure Intercepts

Footnotes
¹⁾ A complete table of assay results from all secondary zones intersected utilizing a 0.2 gpt Au cut off see link here.
²⁾ True widths are estimated based on drill hole geology or comparisons with other on-section drill holes.
³⁾ Composite assay grades presented in summary tables are calculated using an Au grade minimum average of 0.2 gpt or 1.0 gpt as indicated in "Au Cut-off" column of Summary Tables. Maximum internal waste included in any reported composite interval is 3.0 m. The 1.0 gpt Au cut-off is used to define higher-grade "cores" within the lower-grade halo. These cores reflect geology and are comprised of solid quartz veining with notable adularia as opposed to quartz breccia and stockwork zones.

Management Additions and Options Grant

The Company has engaged a full time Los Reyes project manager and a new corporate secretary. Mr. Larry Segerstrom, M.Sc., M.B.A., is a senior mining professional with extensive technical, operational, and business experience, including exploration, mine geology, project management and operations. Mr. Segerstrom served as Chief Operating Officer of Paramount Gold and Silver Corp. and managed the discovery and development of their epithermal gold and silver project in Mexico. He also worked for Freeport-McMoRan Inc., Newmont Corporation, and Phelps Dodge Corp..

Ms. Dianne Szigety has joined the Company as Corporate Secretary. Ms. Szigety is a Chartered Secretary and Fellow of the Chartered Governance Institute of Canada. She is a corporate governance specialist with strong organizational abilities and over 25 years' experience in public company administration.

In connection with these management additions, and pursuant to its Stock Option Plan, Prime granted stock options to key employees to purchase an aggregate of 700,000 common shares of the Company for a period of 5 years from the grant date. 100,000 of the options will vest 1/3 immediately as of the date of grant; 1/3 six months after the date of the grant; and 1/3 twelve months after the date of the grant. 600,000 options will vest 1/3 nine months after the date of grant; 1/3 eighteen months after the date of the grant; and 1/3 twenty-four months after the date of the grant. This stock option grant is subject to acceptance by the TSX Venture Exchange.

QA/QC Protocols and Sampling Procedures

Drill core at the Los Reyes project is drilled in predominately HQ size (63.5 mm), reducing to NQ or BQ size ranges (47.6 mm and 36.5 mm respectively) when required. Drill core samples are generally 1.50 m long along the core axis with allowance for shorter or longer intervals if required to suit geological constraints. Each entire hole is split, and one half is submitted for assay. Sample QA/QC measures of unmarked certified reference materials (CRMs), blanks, and field duplicates as well as preparation duplicates are inserted into the sample sequence and make up approximately 8% of the samples submitted to the lab for each drill hole.

Samples are picked up from the project by Bureau Veritas and transported to their laboratory in Durango, Mexico, for sample preparation. Sample analysis is carried out by Bureau Veritas, with fire assay, including over limits fire assay reanalysis, completed at their Hermosillo, Mexico, laboratory and multi-element analysis in North Vancouver, British Columbia, Canada. Drill core sample preparation includes fine crushing of the sample to at least 70% passing less than 2 mm, sample splitting using a riffle splitter, and pulverizing a 250 g split to at least 85% passing 75 microns (code PRP70-250).

Gold in diamond drill core is analyzed by fire assay and atomic absorption spectroscopy (AAS) of a 30 g sample (code FA430). Multi-element chemistry is analyzed by 4-Acid digestion of a 0.25 g sample split (code MA300) with detection by inductively coupled plasma emission spectrometer (ICP-ES) for 35 elements (Ag, Al, As, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, La, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, S, Sb, Sc, Sn, Sr, Th, Ti, U, V, W, Y, Zn, Zr).

Gold assay technique FA430 has an upper detection limit of 10 ppm. Any sample that produces an over-limit gold value via the FA430 technique is sent for gravimetric finish via method FA-530. Silver analysis by MA300 has an upper limit of 200 ppm. Sample with over limit silver are reanalyzed by fire assay with gravimetric finish (FA530).

Bureau Veritas is an ISO/IEC accredited assay laboratory. Drill core assay results range from below detection to 93.80 gpt gold and 4,224.0 gpt silver. Composite intervals use a cut-off grade of 0.2 gpt gold.

Qualified Person

Kerry Sparkes, P.Geo., Executive Vice President of Exploration, is a qualified person for the purposes of National Instrument 43-101 and has reviewed and approved the technical content in this news release.

Los Reyes Gold and Silver Project

Los Reyes is a district scale low sulphidation epithermal gold-silver project located in a prolific mining region of Mexico. Over $20 million in exploration, engineering and prefeasibility studies have been spent on the project over 2 1/2 decades by previous operators with development plans being held back due to declining gold prices. Historic data coupled with an existing and recently updated resource estimate has provided sufficient understanding to fast-track the project to production. However, there is substantial resource expansion upside based on open extensions of known deposits, multiple untested high priority exploration targets, and only 40% of the known structures systematically explored leaving 10 kilometres of untested strike length. Potential for significant growth of the resource remains strong.

Current Measured and Indicated pit-constrained oxide mineral resources from an April 2020 technical report include 19.8 million tonnes ('mt') containing 633,000 ounces of gold at 1.0 gpt and 16,604,000 ounces of silver at 26.2 gpt plus an additional 7.1 mt Inferred containing 179,000 ounces gold at 0.78 gpt and 6,831,000 ounces silver at 30 gpt.

About Prime Mining

Prime Mining, a member of the TSX Venture 50, is an ideal mix of successful mining executives, strong capital markets personnel and experienced local operators who have united to build a low cost, near-term gold producer at the historically productive Los Reyes project in Mexico. Prime Mining has a well-planned capital structure with significant team and insider ownership.

The TSX Venture 50 is a ranking of the top performers in each of 5 industry sectors on the TSX Venture Exchange over the last year.

ON BEHALF OF THE BOARD OF DIRECTORS

Daniel Kunz
Chief Executive Officer

For further information, please contact:

Daniel Kunz
Chief Executive Officer and Director
Prime Mining Corp.
1307 S. Colorado Ave.
Boise, Idaho 83706
Telephone: 1-208-926-6379 office
email: daniel@primeminingcorp.ca

Andrew Bowering
Executive Vice President and Director
Prime Mining Corp.
1507 - 1030 West Georgia Street
Vancouver, BC, V6E 2Y3
Telephone: (604) 428-6128
Facsimile: (604) 428-6430
E: andy@primeminingcorp.ca

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

Forward Looking Information

Information set forth in this document may include forward-looking statements. While these statements reflect management's current plans, projections, and intents, by their nature, forward-looking statements are subject to numerous risks and uncertainties, some of which are beyond the control of the Company. Readers are cautioned that the assumptions used in the preparation of such information, although considered reasonable at the time of preparation, may prove to be imprecise and, as such, undue reliance should not be placed on these forward-looking statements. There is no assurance the transactions noted above will be completed on the terms as contemplated, or at all. The Company's actual results, programs, activities, and financial position could differ materially from those expressed in or implied by these forward-looking statements.