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Los Filos Mine

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  • Reserves and Resources
  • Technical Report
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The Los Filos mine began commercial production in 2008 and was acquired by Leagold in 2017. The operation consists of two open pit mines – Los Filos and Bermejal – and an underground mine at Los Filos. Production in 2018 totalled 195,362 oz of gold. Leagold’s guidance for 2019 is for 200,000 to 220,000 oz of gold. Los Filos is located 180 km south of Mexico City in the municipality of Eduardo Neri, Guerrero State, Mexico. The property is accessible by paved road and an on-site airstrip and includes 39 concessions covering 148,908 hectares. 

Gold is recovered from crushed and run-of-mine ore via a conventional, low-cost heap leach and ADR (adsorption-desorption-recovery) process. Infrastructure on site includes primary and secondary crushing plants with 18,000 tpd capacity, an overland conveyor system, agglomerator, two heap leach pads (one for ROM and one for crushed ore, with associated conveyors and stackers), two pregnant solution collection ponds (one for each heap), one recirculation pond and two contingency water ponds, and an ADR plant and gold refinery. 

An independent feasibility study completed in January 2019 outlines the potential to increase gold production at Los Filos to more than 400,000 oz/year. Expansion opportunities include development of the Bermejal underground mine, an enlarged Los Filos open pit mine, the re-phasing of the Bermejal open pit into two distinct open pits (Bermejal and Guadalupe) and the construction of a 4,000 tpd carbon-in-leach (CIL) plant.

Geology and Mineralization

Los Filos is located near the center of the Morelos-Guerrero Sedimentary Basin, a thick sequence of Mesozoic platform carbonate rocks. Mineralization is typical of intrusion-related gold-silver skarn deposits and is associated with two early Tertiary granodiorite stocks that were emplaced in carbonate rocks. Mineralization being mined at the Los Filos open pit is associated with a shallowly east-dipping sill and with the upper portion of the east stock. The Los Filos underground is divided into the Los Filos Norte and Sur sectors along the north and south side of the circular west stock. Mineralization in the Bermejal area consists of mineralization along the contact of the Bermejal stock with the carbonate rocks of the Morelos Formation. The Bermejal open pit mineralization is typically at the top or on the flanks of the upper portion of the intrusive. Mineralization extends below the Bermejal open pit and down the steeply dipping to vertical flanks of the intrusive. At the northern end of the intrusive the mineralization is referred to as the Bermejal underground deposit.

Location of the Los Filos Mining Areas and Mineral Deposits

Location of the Los Filos Mining Areas and Mineral Deposits


Mineral Resources and Mineral Reserves

As of October 31, 2018, the Los Filos mine's Proven and Probable Mineral Reserves total 111.3 Mt at 1.22 g/t containing 4.4 Moz gold plus an additional 0.1 Moz Au in Probable leach pad inventory, as shown in the following table:

Los Filos Mineral Reserves (October 31, 2018)

Category Tonnes (kt) Gold Grade (g/t) Gold Ounces (koz)
Proven 36,858 0.76 906
Probable 74,471 1.44 3,457
Proven and Probable 111,328 1.22 4,363
Probable Leach Pad Inventory (recoverable)      114
Total Proven and Probable     4,477


  1. CIM (2014) definitions were followed for Mineral Reserves.
  2. Mineral Reserves for Bermejal Underground were prepared by SRK Consulting (Canada) Inc. Mineral Reserves for all other deposits were prepared by the Los Filos mine and reviewed by SRK.
  3. Mineral Reserves are quoted using a NSR break-even cut-off grade approach with minimum block NSR of $149.4/t for Bermejal underground. Cut-off grade for the Los Filos underground is 2.59 g/t. Mineral reserves for Los Filos, Bermejal and Guadalupe open pits are based on variable break-even cut-offs for ore revenue as generated by process destination and recoveries. Variables for revenue calculation include process cost, recovery, and estimated gold, copper and sulphur grades.
  4. Mineral Reserves are based on Measured and Indicated Mineral Resources.
  5. Metal price assumption for gold was US$1,200/oz.
  6. Tonnage and grade measurements are in metric units. Contained gold are reported as troy ounces.
  7. Summation errors may be present due to rounding.


As of December 31, 2017, the Los Filos mine's Measured and Indicated Mineral Resources total 380.6 Mt at 0.94 g/t containing 11.5 Moz gold and Inferred Mineral Resources of 240.5 Mt at 0.74 g/t containing 5.7 Moz gold as shown in the following table:

Los Filos Mineral Resources (December 31, 2017)

Class Tonnes (kt) Gold grade (g/t) Gold ounces (koz)
Measured 59,119 0.90 1,709
Indicated 321,482 0.94 9,751
Measured & Indicated 380,602 0.94 11,459
Inferred 240,469 0.74 5,739


  1. Mineral resources are inclusive of mineral reserves and do not include dilution.
  2. Mineral resources that are not mineral reserves do not have demonstrated economic viability.
  3. Mineral resources are reported to a gold price of US$1,400/oz and a silver price of US$4.26/oz.
  4. Open pit Mineral resources are defined within pit shells that use variable mining and recovery estimates depending on the geometallurgical domain and whether mineralization is projected to report to crush–leach or is considered typical run-of-mine for processing requirements.
  5. Open pit Mineral resources are reported to variable gold cut-off grades: Los Filos Open Pit 0.198 g/t Au, Bermejal Open Pit of 0.179 g/t Au.
  6. Underground Mineral resources use a mining cost of US$84.78/t for Cut-and-Fill, process cost of US$6.75/t, and a process recovery of 80%.
  7. Mineral resources are reported to a gold cut-off grade: Los Filos Underground of 3.39 g/t Au; Bermejal Underground of 3.0 g/t Au.
  8. Tonnages are rounded to the nearest 1,000 tonnes, grades are rounded to two decimal places for Au, grades for Ag are rounded to two decimal places; rounding as required by reporting guidelines may result in apparent summation differences.
  9. Includes both oxide and sulphide mineralization.


Sources of Technical Information

The Mineral Reserves for the Los Filos Mine are derived from the independent Feasibility Study reported in Leagold’s news release dated January 16, 2019. The Company anticipates filing a technical report prepared in accordance with National Instrument 43-101 – Standards of Disclosure for Mineral Projects (NI 43-101) in early March (Los Filos Technical Report) to support the disclosure of the results of the Feasibility Study.

Qualified Persons

Dr. Gilles Arseneau, P.Geo., Neil Winkelmann, FAusIMM, Timothy Olson, FAusIMM, Eric Olin, RM SME, Neil Lincoln, P.Eng., David Nicholas, P.E. are the Qualified Persons that prepared or supervised the preparation of the information that forms the basis for the written disclosure regarding Los Filos.