Guanaceví is an operational underground silver mine located in the historic silver mining district of Durango in northern Mexico.
The project is owned by Endeavour Silver (EDR), which controls the property through its 100% own Mexican subsidiary Endeavour Gold Corporation.
The company acquired Guanaceví in 2004, and soon after discovered the first high-grade orebody in the property.
It was developed by mechanised underground ramp access, with production commencing in 2005.
Endeavour has identified a total of eight new orebodies along the 5km Santa Cruz vein. The mine currently produces from three ore bodies currently: El Curso, Milache, and Santa Cruz Sur.
The mine provides steady employment to more than 500 people.
In 2023, production is expected to range between 1,150 tonnes per day (tpd) and 1,250tpd.
Location Details
The Guanaceví Silver-Gold Project is located in the northwest region of Durango. The site is around 3.6km west of Guanaceví and 260km northwest of Durango.
The project includes 51 mineral concessions covering an area of 4,171.5 hectares (ha). Endeavour has all the necessary infrastructure at site for functioning.
Guanaceví Project History
Little information is available regarding the extent of historical exploration on the Guanaceví Project with most of the production coming before the 1910 Mexican Revolution.
Before EDR took over, the property produced from three mines without utilising the benefit of any systematic exploration drilling, geological mapping or mine planning production.
In 2003, Pan American Silver conducted an eight-month evaluation programme comprising an extensive, systematic, underground channel sampling and surveying programme as well as three diamond drillholes in the North Porvenir area.
In 2004, Endeavour signed a purchase agreement to acquire Santa Cruz mine and Guanaceví processing plant.
Subsequently, the company signed purchase/lease agreements for acquiring rights to additional prospective areas until December 2006.
In January 2007, Endeavour assumed full control of the day-to-day mining operations to optimise costs and provide more flexibility.
Geology and Mineralisation
The Guanaceví silver-gold district features classic, high-grade silver-gold, epithermal vein deposits featuring low sulphidation mineralisation and adularia-sericite alteration.
Mineralisation at Guanaceví is found in association with an epithermal low sulphidation, quartz-carbonate, fracture-filling vein in a structure that trends approximately N45°W, dipping 55° southwest.
The Santa Cruz vein, the main host of silver and gold mineralisation, is located on the west side of the horst of Guanaceví Formation. The vein stretches for 5km with an average width of 3m.
The mineralised portion is a part of a major fault system which trends towards the northwest direction.
A secondary mineralised vein is also identified subparallel and subjacent to the Santa Cruz vein. Despite being less continuous, the vein is economically significant in the Porvenir Dos and North Porvenir portions of the project.
The minerals encountered in the Santa Cruz vein are argentite-acanthite, limited gold, galena, sphalerite, pyrite, and manganese oxides.
Gangue minerals identified include barite, rhodonite, rhodochrosite, calcite, fluorite, and quartz.
Guanaceví Mineral Reserves
A technical report updating Mineral Resource and Reserve Estimates of the Guanaceví Project was published in December 2022.
According to the technical report, the total measured and indicated mineral resource estimate in the project is 714.4kt containing 12,762 thousand oz (t. oz) of Silver Equivalent (AgEq) at grading of 556g/t, 10,735 t. oz of Silver (Ag) at grading of 467g/t, and 27 t. oz of Gold (Au) at grading of 1.2g/t.
The total mineral reserves (proven and probable) are 1,259.4kt containing 22,969oz of AgEq at grading of 567g/t, 19,287 of Ag at grading of 476g/t, and 46oz of Au at grading of 1.14g/t.
Mining and Ore Processing
Mining at the property is carried out using long-hole stoping method, which was first introduced in 2013 at the mine.
Since 2020, the operations have completely shifted to long-hole stoping from conventional cut and fill method.
The use of long-hole method has increased stope heights from typically 1.8m to up to 17m.
Dilution and hanging wall stability is controlled using 11m long cemented cable bolts.
The mined ore is transferred to the primary crushing circuit of the processing plant which crushes the material to 6inches. It is then transported to the coarse ore bins at the front end of the secondary and tertiary crushing stages.
From the fine ore bins, material is transported to the mills through conveyors.
Recycled solution with sodium cyanide is used to create a pulp of around 60% solids. This solution starts extraction kinetics of silver and gold particles.
Pulp leaving the mills with a 60-65%% solid density is delivered to one or more hydro cyclones to separate the fine particles from the coarser material.
The pulp with fine particles is then sent to the primary thickener. The fine solids passing through 200 mesh are delivered to the grinding thickener where flocculating agents are added to achieve a 50% pulp density at the tank bottom discharge.
The solution undergoes leaching and then, it is delivered to the counter-current decantation (CCD) circuit which consists of five thickeners.
From here, the solution is pumped to the Merrill-Crowe Plant for clarification and precipitation of silver and gold.
In 2021, production was 4.3 million oz of silver and 13,378oz gold.
Contractors involved
The technical report for the Guanaceví Silver-Gold Project, published in 2022, was co-authored by Endeavour Silver and by Hard Rock Consulting, a geologic and mine engineering firm.
Agapito Associates, which specialises in mining and geological engineering, evaluated the existing ventilation systems and suggested improvement options through a site visit.
