Marmato Expansion Highlights 1

A pre-feasibility study on the Marmato Lower Mine Project with an effective date of June 30, 2022 shows robust base case project economics with a post-tax NPV(5%) of $341M using a gold price of $1,600 per ounce.

Marmato Lower Mine Economic Highlights 1*
Gold price (US$/oz) $1,400 $1,500 $1,600 2 $1,700 $1,800
Project NPV @ 5% (after-tax) $150M $246M $341M $438M $533M
Project IRR (after-tax) 16.1% 22.8% 29.7% 37.1% 45.2%

1* Project economics inclusive of precious metal streaming agreement with WPMI. In exchange for the upfront deposits of $175 million, WPMI purchases 10.5% of gold produced from the Marmato mine until 310,000 ounces of gold have been delivered, after which the volume reduces to 5.25% for the life of mine. WPMI will also purchase 100% of silver produced from the Marmato mine until 2.15 million ounces of silver have been delivered, after which the volume reduces to 50% for the life of mine.

2 Base case assumption


@ 3.2 g/t

Au proven and probable gold mineral reserves


@ 3.0 g/t

Au measured and indicated mineral resources


@ 2.4 g/t

Au inferred gold resources

~20 year

Mine life

Based on mineral reserves



Processing capacity


Per year

Gold production


Per oz

LOM average AISC



Lower Mine development capex

1 Please refer to the Reserves and Resources page for scientific and technical disclosure.


Location and History

The Marmato mine is located in the Marmato gold district in the Caldas Department, a mountainous region approximately 80 kilometres south of the city of Medellin, Colombia. The Marmato mine is located by the Pan American Highway and supported by excellent infrastructure, including access to the national electricity grid that runs near the property.

Cerro El Burro, a prominent hill at Marmato, has been mined for nearly 600 years, and was historically divided into three contiguous mining titles with numerous licenses within them, including Zona Alta, Zona Baja, and Echandia. The Maruja Mine in the Zona Baja title was first developed between 1908 and 1925 by the Colombian Mining and Exploitation Company, which mined extensively in the upper levels from the haulage level on Level 18 at 1,160 metres (m) above sea level, and opened the Zancudo mine adit on Level 17, 50 m above Level 18. In 1925, the mines were expropriated and closed. In 1993 Mineros Nacionales S.A.S. began a 300 tonne per day (tpd) underground mine on Level 18. Mining has taken place continuously since then by a series of different owners in the area now known as the Upper Mine in the Zona Baja mining title. In 2012, GCM Mining Corp. (GCM Mining), a publicly listed Canadian company formerly known as Gran Colombia Gold Corp. (Gran Colombia Gold), and currently known as Aris Mining Corporation (Aris Mining), announced the discovery of a deep mineralization trend, now referred to as the Lower Mine, 300 metres below the then known resources in the Upper Mine.

Aris Mining has received approval from the Corporación Autónoma Regional del Caldas (Corpocaldas), the regional environmental authority in Colombia, of the Environmental Management Plan (PMA) which now includes development of the Marmato Lower Mine. This approval allows us to construct a new underground mine to access the wider porphyry mineralization in the Lower Mine, which allows for bulk mining methods.

Geology and Mineralization

Marmato mainly comprises northwest and west-northwest trending veins and veinlets, with intermediate sulfidation epithermal and mesothermal mineralization styles transitioning with depth from the Upper Mine to the Lower Mine. The veins outcrop at the surface, and within Aris Mining’s mining titles, mineralization extends vertically over 1,100 m and remains open at depth and along strike and has a high expansion potential from future underground drilling programs.

The Lower Mine mineralization is characterized by steeply dipping, northwest trending mesothermal fine veinlet porphyry hosted mineralization including quartz, pyrrhotite, chalcopyrite, bismuth sulfide, tellurides, and free gold. The currently defined Lower Mine mineralization covers an area of 950 m northwest-southeast by 350 m northeast-southwest, over a vertical extent of 750 m.

Mining and Processing

The Lower Mine porphyry style mineralization below the 950 m level will be mined using long hole stoping with paste backfill at a targeted mining rate of 4,000 tpd following a quick ramp up period. Ore will be hauled up a new decline to the new Lower Mine processing plant approximately 3 km by road from the Lower Mine. The new processing plant that will be constructed for the Lower Mine includes 4,000 tpd capacity secondary crushing, semi-autogenous and ball mill grinding, gravity concentration, cyanidation of the gravity tailings, a carbon in pulp circuit, and electrowinning and refining to produce gold-silver doré. Metal recoveries are estimated at 95.4% for gold and 57.8% for silver.

Mine Site Layout

The major new Project facilities for the Lower Mine will include the mine portal, decline, crusher, stockpiles, processing facility, two dry stack tailings storage facilities, mining services, accommodation, access roads, power and water management and distribution facilities, and office buildings.