- Updated Maria Bonita resource increased to 403,877 ounces of gold in the Indicated category and 908,477 ounces in the Inferred category, with inferred ounces rising 150% from the 2025 estimate
- Higher-grade resources expanded significantly, including 9.30 million tonnes at 0.75 g/t gold Indicated and 11.11 million tonnes at 0.80 g/t gold Inferred
- The deposit remains open in multiple directions, with ongoing drilling aimed at further expanding the resource across the Cajueiro district in Brazil
- Altamira Gold stock (TSXV:ALTA) last traded at $0.29
Altamira Gold (TSXV:ALTA) announced a significant upgrade to the Mineral Resource Estimate (MRE) for its Maria Bonita porphyry gold deposit at the Cajueiro Project in Mato Grosso, Brazil, marking a substantial increase in both tonnage and contained gold since the maiden estimate released in May 2025.
The updated resource highlights the continued expansion of what is emerging as one of the company’s most important gold assets, with drilling extending the known mineralized system below, west, and northwest of the original resource area. What’s important to note, is that mineralization remains open in several directions, suggesting further growth potential as exploration continues.
This article is a journalistic opinion piece that has been written based on independent research. It is intended to inform investors and should not be taken as a recommendation or financial advice.
Major resource growth
The revised open-pit constrained resource now contains:
- Indicated resources: 25 million tonnes grading 0.50 grams per tonne (g/t) gold, containing 403,877 ounces of gold
- Inferred resources: 70 million tonnes grading 0.41 g/t gold, containing 908,477 ounces of gold
The estimate is reported using a cut-off grade of 0.24 g/t gold and represents a dramatic increase from the maiden resource estimate.
Contained gold in the Inferred category surged by 150%, while contained ounces in the Indicated category increased by 12%. Overall, total resource tonnage has grown by approximately 90%, with contained gold increasing by 82% since the 2025 estimate.
The updated resource was prepared independently by VMG Consultoria e Soluções Ltd. under the direction of Volodymyr Myadzel, PhD, MAIG, with an effective date of September 16, 2026.
Higher-grade zones expand
Beyond the overall growth in the resource base, Altamira reported significant expansion in the deposit’s higher-grade component.
Using a 0.5 g/t gold cut-off, the resource now includes:
- Indicated: 9.30 million tonnes at 0.75 g/t gold containing 225,630 ounces
- Inferred: 11.11 million tonnes at 0.80 g/t gold containing 286,859 ounces
This higher-grade portion of the deposit grew by 56% overall, including a 28% increase in indicated ounces and an 88% increase in inferred ounces.
Management believes this growth strengthens the potential economics of the project while increasing the attractiveness of Maria Bonita as a potential large-scale open-pit mining operation.
Favourable open-pit characteristics
One of the most notable aspects of the revised estimate is the efficient pit design generated during optimization studies.
The updated MRE has been constrained within an optimized open-pit shell and carries a favorable waste-to-mineralized-material ratio of approximately 0.4:1, a metric that could have positive implications for future mining economics.
The estimate utilized a gold price assumption of US$3,300 per ounce, reflecting the average gold price over the three years leading up to August 2026.
Additionally, the resource includes a near-surface saprolite component consisting of:
- Indicated: 1.49 million tonnes at 0.65 g/t gold containing 30,899 ounces
- Inferred: 1.42 million tonnes at 0.38 g/t gold containing 17,172 ounces
Near-surface oxide and saprolite resources are often viewed favorably due to their potentially lower mining and processing costs.
Consistent mineralization supports future growth
Altamira emphasized the consistency of mineralization throughout the Maria Bonita system. The company noted that both porphyry-hosted and tuff-hosted zones display relatively uniform gold grades and distribution patterns.
According to the company, this geological consistency could facilitate the future conversion of inferred resources into higher-confidence resource categories through infill drilling.
The highest gold intercept currently incorporated within the resource model returned 1 metre grading 7.27 g/t gold, while the broader deposit continues to demonstrate large volumes of lower-grade but consistently mineralized material.
Part of a larger gold district
Maria Bonita is located within Altamira’s broader Cajueiro Project, approximately 75 kilometres northwest of Alta Floresta in the state of Mato Grosso. The project benefits from year-round road access, nearby grid power, water availability, and location on open farmland.
The Cajueiro district hosts two independently estimated resource areas:
- Maria Bonita
- Cajueiro Central, located approximately 7 kilometres away
Cajueiro Central currently hosts:
- Indicated Resources of 5.66 million tonnes at 1.02 g/t gold for 185,000 ounces
- Inferred Resources of 12.66 million tonnes at 1.26 g/t gold for 515,000 ounces
Together, the two deposits provide Altamira with a growing resource inventory within a single mining district.
Exploration continues
The Maria Bonita deposit remains open to the west, south, and at depth, and the company is actively drilling the western extension of the system.
Altamira is also evaluating its broader 280-square-kilometre land package, including a newly accessible 58-square-kilometre western sector that may host additional mineralized extensions.
Upcoming exploration plans include:
- Continued step-out drilling west of Maria Bonita
- Trenching programs
- Initial drill testing at the Novo Sonho target
Outlook
The updated resource marks a major milestone for Altamira Gold as it continues to scale the Maria Bonita discovery. With nearly 1.31 million ounces of gold now defined across indicated and inferred categories, a growing higher-grade inventory, favourable open-pit geometry, and ongoing exploration success, Maria Bonita is rapidly establishing itself as a cornerstone asset within the Cajueiro district.
As drilling continues to expand the deposit in multiple directions, investors will be closely watching whether Altamira can further increase resources and advance the project toward future economic studies.
Leadership commentary
“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,” Altamira Gold’s president and CEO, Michael Bennett said in a news release. “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.”
About Altamira Gold Corp.
Altamira Gold Corp. is a junior natural resource company that acquires, explores, develops, and mines mineral properties in Canada and Brazil.
Altamira Gold stock (TSXV:ALTA) opened trading 1.72% higher at $0.29 and has risen 5.36% since the year began.
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