Aris Mining Corporation (TSX: ARIS; NYSE: ARIS) announced on April 17 that construction crews at its Marmato gold mine in Colombia’s Caldas department have completed the underground cross-cut connecting the new surface decline to the existing underground workings, a physical milestone that brings the mine’s bulk expansion directly into its execution phase.
The connection, known in underground mining as a breakthrough, closes the gap between two previously separate development systems: the new surface access decline, built specifically for the Marmato expansion project, and the historic underground workings that have operated for decades. With the systems now physically joined, the mine gains a single continuous underground network from which personnel, ventilation, power infrastructure, and ore haulage can operate in a coordinated, integrated manner.
What Was Built and Why It Matters
The immediate significance of the breakthrough is operational. Aris Mining is constructing a 5,000 tonnes-per-day carbon-in-pulp (CIP) processing plant on surface at Marmato, designed to process ore from the mine’s Bulk Mining Zone, a porphyry-hosted mesothermal gold deposit lying beneath the existing narrow-vein workings. That plant, which represents a fundamental step-change in the mine’s processing capacity compared to the current 1,000 tpd flotation circuit, requires a reliable and high-volume supply of ore from underground.
The cross-cut connection serves as a technical prerequisite for the ongoing expansion, which includes the construction of the 5,000 tpd CIP plant, and the company stated the infrastructure remains on schedule to support the initiation of gold production in the fourth quarter of 2026.
Neil Woodyer, Chair and CEO of Aris Mining, described the milestone as a major step in delivering the company’s expansion plans, noting that the on-schedule connection of the new surface decline to the existing underground development is fundamental to Marmato’s next phase.
Scale, Production Targets, and Capital Deployment
The Marmato expansion is the cornerstone of Aris Mining’s near-term production growth strategy. The company aims to achieve a combined output of approximately 500,000 ounces of gold per year from its Segovia and Marmato operations, with Marmato at steady state expected to produce around 200,000 ounces annually. In 2025, combined output from both mines reached approximately 257,000 ounces, meaning the expansion is targeting a near-doubling of group production.
Sandvik Mining has already secured a large equipment order from Aris Mining to supply underground loaders, trucks, and a range of development, production, and longhole drilling rigs for the Marmato expansion, with the agreement also including a maintenance and repair services contract to support equipment availability and lifecycle performance. That order, valued at approximately SEK 250 million, will see deliveries run from the second quarter of 2026 through mid-2027, directly aligned with the CIP plant commissioning schedule.
The Transition from Narrow Vein to Bulk Mining
The production model being implemented at Marmato represents a structural shift, not merely a capacity addition. The existing operation relies on narrow-vein, labour-intensive extraction, a method that constrains daily throughput and limits economies of scale. The expansion accesses the Bulk Mining Zone using mechanised drill-and-blast stoping, a method suited to the porphyry geology and designed to sustain the higher feed rates the new CIP plant will require.
Industry analysis of the project has noted that fleet selection is not a procurement footnote but a direct enabler of the mining method, the loaders and trucks support higher daily material movement from larger stopes and development drives, while modern drill rigs improve advance rates, drilling accuracy, and cycle consistency.
Financing Structure and Forward Milestones
Aris Mining received a $40 million instalment deposit under its precious metals stream financing following achievement of the 50% completion milestone, with the remaining $42 million instalment deposit payable upon achievement of the 75% completion milestone. The stream structure provides non-dilutive capital aligned to construction progress, reducing balance sheet risk during the build-out phase.
Underground workshop construction, ore storage infrastructure, the main pump station, and field offices are scheduled to commence in the second quarter of 2026, with owner mining rates expected to average approximately 900 tonnes per day through most of 2026, reflecting the throughput capacity of the existing flotation plant, before the CIP plant enters service.
Beyond Marmato, Aris Mining expects a construction decision on its Toroparu gold project in Guyana in early 2027, while environmental studies for the high-grade Soto Norte project in Colombia are being finalised for submission in the second quarter of 2026 to initiate the licensing process. The company’s longer-term stated objective is approximately one million ounces of annual gold production.
Broader Significance
The Marmato breakthrough is a case study in the transition from legacy artisanal-adjacent extraction to industrial-scale mechanised underground mining in Latin America. Marmato is one of Colombia’s oldest gold districts, with continuous mining history stretching back to the colonial era. Converting it into a mechanised bulk operation producing around 200,000 ounces per year would, if delivered, represent a significant contribution to Colombia’s position in Latin American gold production.
At gold prices now trading above $4,700 per ounce, the economics underpinning the expansion are substantially stronger than at the time of original project planning, a structural tailwind that places additional urgency on execution delivery and on-schedule commissioning.
