Vancouver, British Columbia--(Newsfile Corp. - September 21, 2026) - Altamira Gold Corp. (TSXV: ALTA) (FSE: T6UP) (OTCQB: EQTRF) ("Altamira" or the "Company") is pleased to announce the results of an independently prepared and assessed, updated Mineral Resource Estimate ("MRE") for the Maria Bonita porphyry gold deposit within the Company's Cajueiro Project in Brazil. A maiden Mineral Resource Estimate was published on May 5, 2025. Since that time, drilling below and to the west and north-west of the maiden resource has significantly extended the known mineralized system. Mineralization remains open in several directions and additional step-out drilling is ongoing.

Highlights:

• The open-pit resource has been extended to total Indicated Resources of 25Mt @ 0.50g/t gold (403,877oz contained) and Inferred Resources of 70Mt @ 0.41g/t gold (908,477oz). The MRE is reported at a cut-off grade of 0.24 g/t gold.

• This represents a 150% increase in the contained ounces in the Inferred category and a 12% increase in contained ounces in the Indicated category relative to the maiden resource estimate¹.

• The updated MRE has been constrained within an optimised open-pit shell, resulting in a calculated waste to mineralized material ratio of approximately 0.4:1.

• A higher-grade sector of the resource has also grown substantially and, at a 0.5 g/t gold cut-off, now comprises 9.30 Mt at 0.75 g/t gold (225,630 oz) Indicated and 11.11 Mt at 0.80 g/t gold (286,859 oz) Inferred.

• The deposit remains open to the west, south and at depth. Drilling is ongoing on the newly accessible western extension to the resource

CEO, Mike Bennett, commented: "This very significant increase in contained gold ounces at the Maria Bonita gold deposit, together with our existing mineral resource at Cajueiro Central, demonstrates the continued growth of the resource base across the Cajueiro District. Importantly, the Maria Bonita system remains open and continues to expand as drilling progresses.

"Gold mineralization at Maria Bonita continues to be uniform over wide intervals, both within and outside the confines of the porphyry intrusive. Our recent surface mapping has also identified a continuation of the porphyry system to the west, providing an important target for ongoing exploration. We are currently drilling the next round of holes and look forward to providing further updates as the Maria Bonita mineral resource is refined and expanded."

CAJUEIRO PROJECT

The Cajueiro project is located approximately 75km NW of the town of Alta Floresta in the state of Mato Grosso (Figure 1) in central western Brazil. The project is easily accessible by road, lies on open farmland and has grid power and a local water supply (Figure1).

Figure 1: Location of the Company's exploration projects in the Alta Floresta Gold belt.

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The Cajueiro district contains independently estimated mineral resources at Cajueiro Central and Maria Bonita, approximately 7km apart and linked by unsurfaced road.

The Cajueiro Central project has current NI 43-101 resources² of 5.66Mt @ 1.02 g/t gold for a total of 185,000 oz in the Indicated Resource category and 12.66Mt @ 1.26 g/t gold for a total of 515,000 oz in the Inferred Resource category (estimated using a gold price of US$1,500/oz).

The updated mineral resource estimate for Maria Bonita, with an effective date of September 16, 2026, was completed by VMG Consultoria e Soluções Ltda, Belo Horizonte, Minas Gerais, Brazil under the direction of Volodymyr Myadzel PhD, MAIG. The estimate is based on drilling undertaken by Altamira between August 2022 and August 2026 and includes 3,868m of additional drilling, in 11 drill holes, since the maiden mineral resource estimate published in May 2025. (see press release dated May 5, 2025).

Table 1: Drill holes used in mineral resource estimates.

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The parameters used to constrain the pit shell in the mineral resource estimate process are presented in Table 2. A gold price of US$3,300/oz was used, being the average gold price over the last three years to August 2026.

The resource estimations are based on a block model interpolated by the Ordinary Kriging (OK) method, using Micromine software. The block model was created using wireframes and filled with blocks measuring 25 (X) by 25 (Y) by 10 (Z) metres. The radii and the orientation of the search ellipses were determined using standard variograms.

All Inferred Resources and Indicated Resources are defined in accordance with the Canadian Institute of Mining, Metallurgy and Petroleum Definition Standards for Mineral Resources and Mineral Reserves (2014) (the "CIM Standards"). For the Indicated Resources, a wireframe that encompasses the area with a 50×50 and 50×100 metre regular drilling grid was created. For interpolation, an average of 3 holes and 8 composite samples were used. The other blocks were classified as Inferred Resources. The block model was validated in several ways: by running an Inverse Distance Weighted interpolation and comparing the results, and by comparing the means and standard deviations of the block grades to the composite data set.

Based on the geological disposition, an open pit mining configuration was used and, based on metallurgical testwork to date, an agitated leach gold recovery was assumed. Industry standard assumptions on unit costs and other parameters were applied.

Table 2: Maria Bonita independent Mineral Resource estimate parameters.

Open-pit Indicated Resources are 25Mt @ 0.50g/t (403,877oz) and Total Inferred Resources are 70Mt @ 0.41g/t (908,477 oz). These resources include near-surface saprolite Indicated resources of 1.49Mt @ 0.65g/t (30,899oz) and Inferred Resources of 1.42Mt@0.38g/t (17,172oz). The resources were calculated using a 0.24 g/t gold cut-off grade and were estimated for the volume of mineralized material drill tested to date. The uniform style of mineralization and the regular grade distribution is a notable and positive feature which should facilitate future conversion of resources to higher levels of confidence through infill drilling.

Table 3: Maria Bonita Mineral Resource estimate at a 0.24g/t gold cut-off grade.

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1. The effective date of the Maria Bonita Mineral Resource Estimate is September 16, 2026.
2. CIM Standards were followed for the estimation of Mineral Resources.
3. Mineral Resources are estimated at a cut-off grade of 0.24 g/t Au for open-pit fresh-rock mineralization, 0.24 g/t Au for saprolite.
4. Mineral Resources are estimated using a long-term gold price of US$3,300 per ounce.
5. Open pit Mineral Resources are reported within a conceptual open pit
6. Bulk density is 1.68t/m³ for saprolite and 2.63 t/m³ for fresh material based on site measurements on drill core
7. Metallurgical recovery used is 90% for saprolite, and 90% for fresh rock.
8. Numbers may not add due to rounding.
9. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.

A significant higher grade near-surface resource has also been identified, and at a 0.5 g/t gold cut-off comprises total Indicated Resources of 9Mt @ 0.75g/t (for a total of 225,630oz) and Total Inferred Resources are 11Mt @ 0.80g/t (for a total of 286,859oz) (Table 4).

Table 4: Maria Bonita Mineral Resource sensitivity to gold cut-off grade.

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The updated Mineral Resource Estimate represents a substantial increase in the scale of the Maria Bonita deposit compared with the 2025 maiden estimate, with total resource tonnage increasing by 90% and contained gold by 82%. Contained gold in the Indicated category increased by 12%, while contained gold in the Inferred category increased by 150%.

Importantly, the higher-grade component of the resource has also grown materially. At a 0.5 g/t Au cut-off, contained gold increased by 56% overall, including increases of 28% in the Indicated category and 88% in the Inferred category. This growth, together with the presence of a significant near-surface saprolite resource, further strengthens Maria Bonita's potential as a large, potentially open-pittable gold deposit.

Figure 2: Optimised pit outline for the Maria Bonita Mineral Resource showing grade distribution at surface, highlighting the coherent core of the mineralization.

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Figure 3: Geology and optimised pit outline for the Maria Bonita Mineral Resource showing the updated pit outline versus the prior pit based on the maiden mineral resource.

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The Maria Bonita porphyry gold deposit shows remarkably consistent grade character within both the porphyry and tuff hosted sectors of the resource. The peak gold assay value recorded in the drilling to date, within the mineral resource is 1m @ 7.27g/t Au.

The Maria Bonita porphyry is part of a district-scale, mineralizing event exposing different levels of the mineralizing system. The Company continues to evaluate the entire concession area of 280km² including the newly accessible 58km² western areas which include the westward extension of the Maria Bonita mineral resource where step-out drilling is now underway. Trenching and initial drill testing of the Novo Sonho target are also planned in the short term.

Qualified Persons

The updated Mineral Resource Estimate for Maria Bonita was completed by VMG Consultoria e Soluções Ltda., Belo Horizonte, Minas Gerais, Brazil, under the direction of Volodymyr Myadzel, PhD, MAIG, a consultant to the Company and a Qualified Person as defined by National Instrument 43-101, who was responsible for the Mineral Resource Estimate.

Fernando Benegas, FAusIMM, a consultant to the Company and a Qualified Person as defined by National Instrument 43-101, supervised the preparation of, and has reviewed and approved, the technical information contained in this news release.

Further details supporting the geological model, estimation procedure and block modelling will be available in a National Instrument 43-101 Technical Report authored by Volodymyr Myadzel, PhD, MAIG, of VMG Consultoria e Soluções Ltda of Belo Horizonte, Minas Gerais, Brazil. The report will be posted under the Altamira profile at www.sedarplus.ca within 45 days from the date of this news release.

About Altamira Gold Corp.

The Company is focused on the exploration and development of gold projects within western central Brazil, strategically advancing four projects spanning over 90,000 hectares within the prolific Juruena Gold Belt-an area that has historically yielded over 6 million ounces of placer gold³. Leading the portfolio is the Maria Bonita project, a highly prospective bulk tonnage asset with a mineral resource published under NI 43-101 as outlined in this press release. In addition, the Cajueiro Central deposit contains a resource estimated under NI 43-101 of 185,000 ounces of gold in the Indicated category (5.66Mt @ 1.02 g/t) and an additional 515,000 ounces in the Inferred category (12.66Mt @ 1.26 g/t)².

With abundant identified opportunities, newly accessible ground and a track record of significant discoveries, the Company is well-positioned to unlock further value across its expansive land package.

¹ NI43-101 Technical Report, Mineral Resource for the Maria Bonita Prospect: VMG Consultoria, Belo Horizonte, Minas Gerais, Brazil. 12^th June 2025; Author V. Myadzel

²NI 43-101 Technical Report, Cajueiro Project, Mineral Resource Estimate: Global Resource Engineering, Denver Colorado USA, 10^thOctober 2019; Authors K. Gunesch, PE; H. Samari, QP-MMSA; T. Harvey, QP-MMSA

³Juliani, C. et al; Gold in Paleoproterozoic (2.1 to 1.77 Ga) Continental Magmatic Arcs at the Tapajós and Juruena Mineral Provinces (Amazonian Craton, Brazil): A New Frontier for the Exploration of Epithermal-Porphyry and Related Deposits. Minerals 2021, 11, 714. https://doi.org/10.3390/min11070714

On Behalf of the Board of Directors,

Neither 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.

The securities described herein have not been registered under the U.S. Securities Act or any state securities laws and may not be offered or sold in the United States absent registration or an applicable exemption from registration requirements under the U.S. Securities Act and any applicable state securities laws.

Forward-Looking Statements

Certain information contained herein constitutes "forward-looking information" under Canadian securities legislation. Forward-looking information includes, but is not limited to, statements regarding the Company's planned exploration activities at Maria Bonita, including soil and stream-sediment sampling, geological mapping, geophysical interpretation, drill-target definition and future drilling; the timing and scope of such programs; the interpretation of geochemical and geophysical anomalies; the potential identification of primary gold sources and intrusion-related mineralization; the potential extension of the current Maria Bonita mineral resource to the west; and the Company's ability to obtain or maintain the necessary surface access, permits and regulatory approvals. Generally, forward-looking information can be identified by the use of forward-looking terminology such as "will", "intends" or variations of such words and phrases or statements that certain actions, events or results "will" occur. Forward-looking statements are based on the opinions and estimates of management as of the date such statements are made and they are subject to known and unknown risks, uncertainties and other factors that may cause the actual results to be materially different from those expressed or implied by such forward-looking statements or forward-looking information, including the receipt of all necessary regulatory approvals. Although management of the Company has attempted to identify important factors that could cause actual results to differ materially from those contained in forward-looking statements or forward-looking information, there may be other factors that cause results not to be as anticipated, estimated or intended. There can be no assurance that such statements will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on forward-looking statements and forward-looking information. The Company will not update any forward-looking statements or forward-looking information that is incorporated by reference herein, except as required by applicable securities laws.

Quality Assurance/Quality Control

Drill holes commence in HQ diameter (63.5mm) and proceed to the base of weathering where core diameter is reduced to NQ (47.6mm). Logging and sampling are completed at a secure Company facility located on site. Drill core is cut in half on site by a saw cut or slicer (in soft saprolite). Until dispatch, samples are stored under the supervision the Company's exploration office. The samples are couriered to the assay laboratory using a commercial contractor. Pulps are returned to the Company and archived.

For all drilling, half core is submitted to SGS Geosol, a leading commercial laboratory in Brazil and analysed for gold by 50g fire assay, plus a suite of other elements by the ICP atomic absorption method, using standard laboratory procedures. Soil and rock chip samples follow the same analytical protocol.

Quality control of drill hole assays follows normal industry procedures of inserting control samples randomly into the submitted batch, comprising field duplicates, independent reference samples and "blank" samples. Selected batches of sample pulps are periodically resubmitted to a third-party laboratory to check the main laboratory precision and accuracy. Drill holes results are quoted as down-hole length weighted intersections. True widths have not yet been determined.

Additional information regarding the Company data verification processes is set out in the NI 43-101 Technical Report, Maria Bonita Prospect, June 2025, which can be found on the Company's website¹.

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Source: Altamira Gold Corp.