Montreal, Quebec--(Newsfile Corp. - June 16, 2026) - Mosaic Minerals Corporation (CSE: MOC) ("Mosaic" or the "Company") is pleased to announce the start of its summer exploration campaign on its Golden Island gold property. Field crews are currently deployed on site to begin preliminary work for the season.

Preparatory Work and Stripping

A team is currently in the field to begin the first phase of the campaign. Initial work will consist of clearing access roads and cleaning historical trenches. These preparatory steps will allow the Company's geologists to identify priority areas for prospecting and stripping before the arrival of heavy machinery expected in the coming days.

Mapping, Sampling, and Exploration

As soon as access roads and trenches are cleared, the geological team will conduct an initial surface sampling program, including groove sampling, as well as a complete geological survey. The campaign, officially scheduled to run from June 16 until the end of July, will include the following steps:

• Precise Location: GPS survey of all historical trenches, the original shaft, the underground gallery entrance, and the old drill collars drilled by SOQUEM.
• Underground Evaluation: Safe walkthrough and sampling of the existing gallery to catalog and analyze all internal mineralized structures.
• Targeted Exploration: Intensive exploration in the immediate vicinity of the main zone.

Link To Map 1

Bulk Sampling Program (Mini-Bulk)

To better assess the nature of the mineralization at Golden Island, the Company also plans to collect mini-bulk samples of approximately 500 kg each from the various identified areas. These samples will be processed in a small pilot plant to evaluate the ratio of coarse gold to overall mineralization. This method will act as a large-scale metal screening analysis, thus providing a much more accurate representation of the system's gold content.

"We are eager to rediscover the potential of Golden Island. Historical work provides us with excellent targets, and our rigorous approach, including mini-bulk testing, will allow us to fully understand the dynamics of coarse gold on the property," concluded Jonathan Hamel, CEO of Mosaic.

Historical Work and Resources

Multiple exploration programs have been carried out in previous years. Notably, in 1982, SOQUEM completed a short program of 8 drill holes (1,150 meters), three of which were drilled in the main zone. (See Table 1)

Table 1 – Drilling Results - SOQUEM 1982 (GM38876)

It should also be noted that drill hole 82-5, located approximately 1 km northwest of the main zone, intersected a 4.7-meter interval grading 1.31 g/t Au. This drill hole is associated with the same magnetic anomaly as the one linked to the main shaft.

2024 Exploration Campaign

An exploration session using an underwater drone allowed for the clear identification, through photography, of quartz veins and veinlets within the gallery walls. The rock's strength has ensured that the gallery has not collapsed, even after nearly a century. Sampling work carried out in the fall of 2024 focused on a set of gold-bearing veins located southeast of the old mine shaft. A total of 25 selected samples were collected (see Table 2) from both the old trenches and outcrops.

During the 2024 sampling, the presence of numerous quartz veins was noted in the vicinity of the trenches and the main shaft. The gold-bearing zone is in contact with a strong magnetic anomaly several kilometers long, running in a NW-SE direction.

Table 2 – Best Sample Results (Autumn 2024)

Qualified Person

The scientific and technical information of Mosaic Minerals Corporation included in this press release has been reviewed and approved by Robert Gagnon, P.Geo, Director of Mosaic Minerals and qualified person under National Instrument 43-101 respecting information concerning mining projects ("Regulation 43-101").

About Mosaic Minerals Corporation

Mosaic Minerals Corp. is a Canadian mining exploration company listed on the Canadian Securities Exchange (CSE: MOC). The Company is developing the Golden Island (Au), Amanda (Au) and Gaboury (Ni) projects located in Abitibi and James Bay (Quebec).

This release contains certain "forward-looking information" under applicable Canadian securities laws concerning the Arrangement. Forward-looking information reflects the Company's current internal expectations or beliefs and is based on information currently available to the Company. In some cases, forward-looking information can be identified by terminology such as "may", "will", "should", "expect", "intend", "plan", "anticipate", "believe", "estimate", "projects", "potential", "scheduled", "forecast", "budget" or the negative of those terms or other comparable terminology. Assumptions upon which such forward-looking information is based includes, among others, that the conditions to closing of the Arrangement will be satisfied and that the Arrangement will be completed on the terms set out in the definitive agreement. Many of these assumptions are based on factors and events that are not within the control of the Company, and there is no assurance they will prove to be correct or accurate. Risk factors that could cause actual results to differ materially from those predicted herein include, without limitation: that the remaining conditions to the Arrangement will not be satisfied; that the business prospects and opportunities of the Company will not proceed as anticipated; changes in the global prices for gold or certain other commodities (such as diesel, aluminum and electricity); changes in U.S. dollar and other currency exchange rates, interest rates or gold lease rates; risks arising from holding derivative instruments; the level of liquidity and capital resources; access to capital markets, financing and interest rates; mining tax regimes; ability to successfully integrate acquired assets; legislative, political or economic developments in the jurisdictions in which the Company carries on business; operating or technical difficulties in connection with mining or development activities; laws and regulations governing the protection of the environment; employee relations; availability and increasing costs associated with mining inputs and labour; the speculative nature of exploration and development; contests over title to properties, particularly title to undeveloped properties; and the risks involved in the exploration, development and mining business. Risks and unknowns inherent in all projects include the inaccuracy of estimated reserves and resources, metallurgical recoveries, capital and operating costs of such projects, and the future prices for the relevant minerals. The Canadian Securities Exchange does not accept responsibility for the adequacy or accuracy of this release.

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Source: Mosaic Minerals Corporation