20-F/A: Aura Minerals Updates Serra Grande Gold Resources & Reserves

Aura Minerals Inc. filed an amendment to its annual report, disclosing updated S-K 1300 compliant Mineral Resource and Reserve estimates for its Mineração Serra Grande Gold Project in Brazil, showing robust economics and a 10-year mine life.

Summary

• Aura Minerals Inc. (AUGO) filed an Amendment No. 4 to its Form 20-F for the fiscal year ended 2025, specifically to include the S-K 1300 Technical Report Summary for the Mineração Serra Grande (MSG) Project in Gois, Brazil.
• Aura Minerals beneficially owns 100% of the MSG Project, having acquired it from AngloGold Ashanti (AGA) in December 2025.
• The MSG Project has a total Mineral Reserve of 11.93 Mt at 1.96 g/t Au, containing 752.77 koz of gold, supporting a 10-year mine life.
• The project's post-tax Net Present Value (NPV) is estimated at US$ 588.1 million at a 5% discount rate, based on a gold price of US$ 3,515/oz.
• Total Open Pit exclusive Mineral Resources (Measured + Indicated) are 5.86 Mt at 1.25 g/t Au (236.25 koz), with an additional 8.91 Mt at 1.16 g/t Au (332.24 koz) in Inferred resources.
• Total Underground exclusive Mineral Resources (Measured + Indicated) are 6.40 Mt at 4.19 g/t Au (862.54 koz), with an additional 13.37 Mt at 4.03 g/t Au (1,733.44 koz) in Inferred resources.
• The metallurgical plant, commissioned in 1989, has an annual processing capacity of 1.5 Mtpa with a 95% gold recovery rate, utilizing CIL and gravimetric circuits.
• Operating costs are summarized as US$ 21.30/t ore for Open Pit Mining, US$ 67.12/t ore for Underground Mining, US$ 20.39/t ore for Processing, and US$ 3.65/t ore for G&A.
• The project is operating under an environmental license currently undergoing revalidation, with a Conduct Adjustment Agreement (TAC) executed on November 27, 2025, to ensure operational continuity.

Sentiment

Score: 8

Explanation: StockSavvy.ai views this as a strong positive update, reflecting robust economics, significant reserves, and a clear path for future growth, despite some minor QA/QC issues that require further investigation.

Positives

• The project demonstrates strong financial performance with a post-tax Net Present Value (NPV) of US$ 588.1 million at a 5% discount rate, based on a gold price of US$ 3,515/oz.
• A significant total Mineral Reserve of 11.93 Mt at 1.96 g/t Au, containing 752.77 koz of gold, supports a robust 10-year mine life.
• The metallurgical plant is mature and efficient, operating at an annual capacity of 1.5 Mtpa with a consistent 95% gold recovery rate.
• The operation has substantial exclusive Mineral Resources, including 236.25 koz Au (Measured + Indicated) for open pit and 862.54 koz Au (Measured + Indicated) for underground, indicating future growth potential.
• The operation is considered viable and compliant with environmental regulations, supported by an ongoing license revalidation and a Conduct Adjustment Agreement (TAC).
• The project shows robustness against Capital Expenditure (Capex) overruns, safely absorbing potential fluctuations in initial capital expenditure.
• Dam decharacterization works were fully completed in July 2025, demonstrating progress in environmental management.

Negatives

• Duplicate gold assay results show moderate to low precision, ranging between 46% and 90% below the 15% precision limit, which is a known issue requiring further investigation.
• The gold price used for Mineral Reserve estimation (US$ 2,600/oz) is conservative compared to the price used for Reasonable Prospects for Economic Extraction (RPEE) (US$ 3,100/oz) and the current spot price (US$ 5,322/oz), potentially understating reserve value.
• The project's Net Present Value (NPV) is highly sensitive to fluctuations in commodity pricing and operational expenditures (OPEX), with a 20% drop in price severely constraining cash generation.
• The maximum number of samples applied in Ordinary Kriging (40 samples) might be too high, potentially leading to a significant smoothing effect on the grade estimate, which could impact resource accuracy.

Risks

• Commodity Price Volatility: The project's economic viability is highly sensitive to fluctuations in gold prices, with a 20% drop potentially severely constraining cash generation.
• Operational Expenditure (OPEX) Control: High sensitivity to OPEX demands strict governance of operating costs to maintain profitability.
• Geological and Grade Continuity: The gold duplicate results show moderate to low precision, indicating high variability in gold grades, which requires further investigation to ensure accurate resource characterization.
• Mineral Resource Estimation Accuracy: The potential for a significant smoothing effect on grade estimates due to the high maximum number of samples used in Ordinary Kriging could impact the accuracy of Mineral Resource estimates.
• Environmental Permitting and Compliance: While currently operating under a revalidating license and a Conduct Adjustment Agreement (TAC), the continuity of operations is conditioned upon full compliance with the TAC and ongoing environmental programs.
• Hydrogeological Conditions: Geotechnical and hydrogeological considerations during mining could differ from assumptions, potentially impacting operations.
• Mining Method Performance: Failure of mining methods to operate as anticipated could affect production and costs.
• Plant and Equipment Performance: Failure of the processing plant, equipment, or processes to operate as anticipated could impact recovery rates and throughput.
• Labor Disputes and Accidents: Standard mining industry risks such as accidents and labor disputes could disrupt operations.
• Tax Rate Changes: Changes to Brazilian tax laws could impact the project's financial performance.
• Unrecognized Environmental Liabilities: The assessment of environmental liabilities was not within the scope of this report, leaving potential unrecognized liabilities.

Future Outlook

Aura Minerals believes there is significant exploration upside in the project area to expand and improve Mineral Resources, which could extend the project's Life of Mine (LOM). The company plans continued exploration and drilling to further delineate mineralization in current and near-mine targets. Continuous improvement efforts are focused on increasing throughput and reducing tailing grade at the metallurgical plant. The project's LOM production schedule supports a 10-year mine life, with ongoing efforts to maintain environmental compliance and update risk management instruments.

Management Comments

• Aura strongly believes that there is an exploration upside in the Project area to expand and improve Mineral Resources, and consequently, the future Projects Life of Mine (LOM).

Industry Context

StockSavvy.ai notes that the gold market is experiencing significantly elevated prices, with a spot price of US$ 5,322/oz as of March 3, 2026, reaffirming gold's position as a primary safe-haven asset. While long-term projections indicate a gradual correction to around US$ 3,515/oz, these prices remain substantially above historical averages. This favorable market environment provides a strong backdrop for Aura Minerals' Mineração Serra Grande Project, whose robust economic analysis is based on a conservative long-term gold price of US$ 3,515/oz, suggesting resilience even if prices moderate from current highs. The project's established operations and focus on resource expansion align with broader industry trends of optimizing existing assets and seeking organic growth in a strong commodity cycle.

Comparison to Industry Standards

• The project's metallurgical plant operates at 1.5 Mtpa with 95% gold recovery, which is considered efficient and aligns with good industry practices for CIL and gravimetric circuits.
• The data management and QA/QC protocols for drilling and sampling are compliant with industry best practices, contributing to secure and valid data for Mineral Resource estimation.
• The use of S-K 1300 standards for Mineral Resource and Reserve reporting ensures compliance with U.S. SEC regulations, aligning with international best practices for transparency in mineral disclosure.
• The mine closure concept is integrated with the project life cycle and aligned with national legal requirements, AngloGold Ashanti's corporate standard (PN-1481), ANM Resolution N 68/2021, and international best practices of the ICMM and IBRAM Mine Closure Planning Guide.
• The project's economic analysis, with a post-tax NPV of US$ 588.1 million and AISC of US$ 1,347.28/oz, appears competitive within the gold mining sector, especially considering the conservative gold price assumption for reserves (US$ 2,600/oz) compared to the long-term forecast (US$ 3,515/oz). No specific comparable companies or projects are detailed in the filing for a direct comparison.

Stakeholder Impact

• Shareholders: Positive impact due to robust economic analysis, significant Mineral Resources and Reserves, and a long mine life, indicating potential for sustained returns.
• Employees: Continued employment and potential for growth given the project's long-term viability and exploration upside.
• Local Communities (Crixás, Gois State): Positive impact through job creation, strengthening of the local economy, and use of existing infrastructure; ongoing environmental education and social communication programs aim to maintain dialogue and promote awareness.
• Regulatory Authorities (ANM, SEMAD): Ongoing engagement through environmental licensing, compliance with the Conduct Adjustment Agreement (TAC), and adherence to Brazilian mining and environmental regulations.
• Previous Owner (AngloGold Ashanti): Receives a 3% NSR royalty on gold ounces produced from the currently identified Mineral Resource.
• Landowners: Receive NSR participation varying from 0.75% to 2.0% for specific orebodies.

Next Steps

• Continued exploration and drilling to expand current mines and near-mine targets.
• Additional drilling program to check open high-grade zones and improve geological model confidence for resource classification upgrades.
• Implementation of a robust Screen Fire Assay analysis program to characterize gold grain size and address moderate to low precision in duplicate QA/QC sample results.
• Modeling a new low-grade mineralization zone based on updated marginal cut-off grades, given the current increase in gold selling prices.
• Conducting a study related to the search neighboring strategy for ordinary kriging to assess the influence of the maximum number of samples on grade estimates and potential smoothing effects.
• Maintaining continuous and integrated execution of environmental control actions and monitoring programs as per the Unified Operating License N 88/2023 and the Conduct Adjustment Agreement (TAC).
• Ensuring continuity and traceability of environmental monitoring programs, with periodic critical analysis of results and timely corrective measures.
• Keeping environmental risk management instruments updated and addressing technical demands from the environmental agency for license renewal.

Key Dates

Recommendation

The Mineração Serra Grande Project demonstrates strong financial fundamentals with a post-tax NPV of US$ 588.1 million and competitive AISC of US$ 1,347.28/oz, supporting a 10-year mine life. The updated Mineral Resource and Reserve estimates, coupled with significant exploration upside, suggest long-term value creation. While there are minor QA/QC issues to address and sensitivity to commodity prices, the project's established operations, efficient processing plant, and proactive environmental management make it an attractive investment. The conservative gold price used for reserves further de-risks the valuation, indicating potential for upside if gold prices remain elevated.

Keywords

Aura Minerals, AUGO, Mineração Serra Grande, Gold Mining, SEC Filing, 20-F/A, S-K 1300, Mineral Resources, Mineral Reserves, Brazil, Gois, Gold Exploration, Mining Operations, Economic Analysis, NPV, AISC, Environmental Compliance, Tailings Management, Orogenic Gold Deposit