Our Mulatos Mine is our foundation having been acquired for $10 million in 2003 and grown to become a consistent gold producer and significant cash flow generator.  To date, Mulatos has generated approximately $420 million in free cash flow

Slide table

Mulatos Mine

Ownership 100%
Location Sonora, Mexico
Status Operating
Operation Open Pit, heap leach & high grade mill
Commodity Gold
Annual Operating Data 2018A 2019A
Production oz Au 175,500 142,000
Cost of Sales2  US$/oz $989  $982
Total Cash Costs1 US$/oz $786 $784
Mine-Site All-in Sustaining Costs1 US$/oz $855 $868
(g/t Au)
Proven & Probable Reserves 41,172 1.18 1,563,000
Measured & Indicated Resources3 74,238 1.09 2,608,000
Inferred Resources 9,300 0.90 269,000

2Cost of sales include mining and processing costs, royalties and authorization.

3M&I Resources exclusive of Reserves

Please see 2019 year end Reserves and Resources statement for additional detail


Since the start of production, Mulatos has generated approximately $420 million in free cash flow.


Mulatos produced its two millionth ounce of gold in March 2019.


The Mulatos District has a six year mineral reserve life as of December 31, 2019.



The 100% owned Mulatos Mine is a conventional open-pit, heap-leach operation with gold recovered through a carbon-in-column circuit. The project was originally contemplated as a 10,000 tpd operation though through various expansions and productivity improvements over the years, today operates at a throughput rate of over 20,000 tpd.

Based on Proven and Probable Mineral Reserves at the end of 2019 and current throughput rates, Mulatos has an expected mine life of approximately six years.

In 2019, the Company achieved another major milestone, producing its two millionth ounce at Mulatos, marking the end of the 5% NSR royalty at Mulatos after which no third party royalty is payable on production at the mine. 


The Mulatos Mine is located within the Salamandra Concessions in the Sierra Madre Occidental mountain range in the east-central portion of the State of Sonora, Mexico. The mine is approximately 220 kilometres ("km") by air east of the City of Hermosillo, and 300km south of the border between the United States of America and Mexico. The Salamandra Concessions are 100% owned by Alamos and consist of 30,356 hectares of mineral concessions, in 44 discrete concessions. These cover the Mulatos deposit, the satellite gold systems known as Cerro Pelon, La Yaqui, El Realito, El Carricito, El Halcon, Las Carboneras, El Jaspe, Puebla, Los Bajios, and La Dura, and other prospective exploration targets. Mineral rights for all the Salamandra Concessions are controlled by Minas de Oro Nacional, S.A. de C.V., a wholly owned subsidiary of Alamos.


The Mulatos project was acquired in February 2003 for $10 million. Following completion of a feasibility study, construction began in the third quarter of 2004. The mine was built at a cost of approximately $74 million with the first gold pour completed 2005 followed by commercial production on April 1, 2006. The operation was initially contemplated as a 10,000 tpd operation though with future expansion potential in mind, major components of Mulatos including the crusher/conveyor and gold recovery plant were sized for a 15,000 tpd operation. A number of expansions and productivity improvements have taken place through the years and daily crusher throughput is now capable of exceeding 20,000 tpd.



The Mulatos District occurs within the Sierra Madre Occidental volcanic province. Deposits in the district are hosted within a mid-Tertiary dacitic to rhyodacitic volcanic dome complex and are considered high-sulphidation, epithermal deposits. Gold mineralization is closely associated with silicic and advanced argillic alteration occurring near the upper contact of a rhyodacite porphyry and in overlying dacite flows and volcaniclastic rocks. All lithologic units of the dome complex are intensely altered. Alteration assemblages are typical of high-sulphidation deposits and show zonation patterns from distal propylitic alteration through illite to kaolinite to dickite/pyrophyllite to pervasive, vuggy silica alteration. Gold is predominantly hosted within this silicic alteration. The altered and mineralized units are locally overlain by a thick section of unaltered volcanic rocks that are believed to be post-mineral in nature. Tilting and post-mineral normal faulting associated with late Tertiary extensional (basin and range) tectonics have affected both the mineralized flow dome complex and overlying volcanic rocks. North-northwest and northeast trending faults cut all rocks in the Mulatos area. The Mulatos mine is exposed in the footwall uplift of the Mulatos extension fault.

The Mulatos deposit proper is composed of the contiguous Estrella, El Salto, Mina Vieja, and Puerto del Aire resource areas. The Escondida deposit is the faulted extension of the Mina Vieja and El Salto deposits and mineralization is believed to be continuous to the northeast to the Gap, El Victor and San Carlos mineralized areas. Although zones are often bounded by post-mineral faults, together they form a trend of 2.7km of gold mineralization starting at the north end of the Estrella pit to the San Carlos deposit.

Within the larger Salamandra Concessions, and generally within 20km from the Mulatos deposit, geologically similar high-sulfidation gold deposits, occurrences, or prospects are known. The principal ones, some of which are in the process of being evaluated and/or drill-tested, are: Cerro Pelon, La Yaqui, El Realito, El Carricito, El Halcon, Las Carboneras, El Jaspe, Puebla, Los Bajios, and La Dura.


Gold deposits of the Mulatos district are high-sulphidation, epithermal, disseminated gold deposits. Precious metal mineralization at Mulatos is associated with intense silicic alteration (mostly vuggy silica), advanced argillic alteration, and the presence of hydrothermal breccias. The original protoliths (dacite porphyry flow/tuff, coarse grained volcaniclastic rocks, breccias), as indicated by surface mapping and core drilling, may have contained in the order of 2-3 percent sulphide as pyrite with various amounts of enargite and tetrahedrite.

Gold mineralization occurs primarily within areas of pervasive silicic alteration of the volcanic host rocks, and to a lesser extent, within advanced argillic alteration assemblages proximal to silicic alteration. The gold-bearing advanced argillic zones are dominated by pyrophyllite or dickite alteration. Silicic rocks host approximately 80 percent of the contained gold within the deposit.

Staude (2001) describes three main mineralization assemblages. From oldest to youngest they are: 1) quartz + pyrite + pyrophyllite + gold; 2) quartz + pyrite + kaolinite + gold + enargite; 3) kaolinite + barite + gold. Free gold is commonly found in hematite-filled fractures. Gold also occurs in pyrite, as gold/silver telluride minerals, and possibly as a solid solution in some copper sulphide minerals. Supergene oxidation and perhaps remobilization and secondary enrichment of gold have been ongoing since the post-mineral volcanic cover was removed.

Gold mineralisation exists in oxide, mixed oxide/sulphide, and sulphide ore types, with pyrite as the primary sulphide mineral. The deposits are amenable to cyanidation in all ore types, but gold extraction decreases with decreasing levels of oxidation.


Mining and processing at Mulatos is via conventional open-pit mining methods followed by a four stage crushing circuit after which it is conveyed and stacked and leached on the heap leach facility. Current throughput rates exceed 20,000 tpd. Gold is ultimately recovered through a carbon-in-column circuit, and an electrowinning and refining plant.


Mining at Mulatos is by way of conventional open pit methods. The open pit mining is a typical drill, blast, load haul operation with mining in the main pit being done with 9 metre ("m") bench heights. The mine switched from a 6m to 9m bench height to improve productivity. It is anticipated that a 3m bench will be used at Yaqui and Pelon to improve selectivity. 


Lower grade from the open pit is processed through four stages of crushing to a target size of 95 percent minus 3/8 inches. Run-of-mine ore is delivered to the primary crusher feed hopper by rear-dump haul trucks. Ore is first crushed to 80%, passing a 15-centimetre screen in the primary jaw crusher. Primary crushed ore is then fed to the secondary cone crusher after which it is conveyed to scalping screens where oversized ore is conveyed to the coarse ore stockpile while undersized ore is discharged and conveyed to the fine ore stockpile.

Ore is withdrawn from the coarse ore stockpile by two variable speed apron feeders and conveyed to three tertiary crushers, each with a dedicated vibrating feeder. The tertiary crushed ore is conveyed to vibrating screen where oversized ore is transferred to and crushed in the single quaternary cone crusher. The quaternary crushed ore is discharged onto the crusher conveyor and recirculated back to the vibrating screen. The undersized screened ore flows to the fine ore collection conveyor, ultimately to the fine ore stockpile. This process has "closed the crushing circuit" such that oversized material is re-circulated through the crushing process and approximately 95% of the ore passes through the 3/8-inch screen to be delivered to the pad. The higher consistency of the crushed product has positively impacted recoveries.

After crushing, lime and cement are added and the ore is conveyed to a pair of agglomerators. Once agglomerated, the ore is delivered to the leach pad for stacking and leaching via a series of portable conveyors ending with a radial stacking conveyor. The heaps are underlain by an impermeable plastic layer on top of a layer of compacted clay.

To extract the gold from the ore, a low-concentration cyanide solution is applied to the ore on the leach pad using a low-pressure irrigation sprinkler system. Alamos installs inter-lift liners on the pad on a periodic basis to reduce percolation time, which decreases the time it takes to extract and produce gold from each lift of the heap.

The resulting gold-bearing solution is channelled to the pregnant solution pond and is then pumped to the carbon-in-column circuit, where gold is recovered from the solution. The barren solution is then recirculated to the heap with added cyanide. Dore bars are produced on site and transferred to a third-party refinery for final recovery of gold and minor amounts of silver.

Technical Information and Cautionary Notes on non-GAAP Measures and Additional GAAP Measures

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Non-GAAP Information

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Reconciliation of non-GAAP and additional GAAP measures

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Note to U.S. Investors

Alamos prepares its disclosure in accordance with the requirements of securities laws in effect in Canada, which differ from the requirements of U.S. securities laws. Terms relating to mineral resources in this website are defined in accordance with National Instrument 43-101 – Standards of Disclosure for Mineral Projects under the guidelines set out in the Canadian Institute of Mining, Metallurgy, and Petroleum Standards on Mineral Resources and Mineral Reserves. The United States Securities and Exchange Commission (the “SEC”) permits mining companies, in their filings with the SEC, to disclose only those mineral deposits that a company can economically and legally extract or produce. Alamos may use certain terms, such as “measured mineral resources”, “indicated mineral resources”, “inferred mineral resources” and “probable mineral reserves” that the SEC does not recognize (these terms may be used in this website and are included in the public filings of Alamos, which have been filed with the SEC and the securities commissions or similar authorities in Canada).

Cautionary non-GAAP Measures and Additional GAAP Measures

Note that for purposes of this section, GAAP refers to IFRS. The Company believes that investors use certain non-GAAP and additional GAAP measures as indicators to assess gold mining companies. They are intended to provide additional information and should not be considered in isolation or as a substitute for measures of performance prepared with GAAP.
Additional GAAP measures that are presented on the face of the Company’s consolidated statements of comprehensive income include “Mine operating costs”, “Earnings from mine operations” and “Earnings from operations”. These measures are intended to provide an indication of the Company’s mine and operating performance. “Cash flow from operating activities before changes in non-cash working capital” is a non-GAAP performance measure that could provide an indication of the Company’s ability to generate cash flows from operations, and is calculated by adding back the change in non-cash working capital to “Cash provided by (used in) operating activities” as presented on the Company’s consolidated statements of cash flows. “Free cash flow” is a non-GAAP performance measure that is calculated as cash flows from operations net of cash flows invested in mineral property, plant and equipment and exploration and evaluation assets as presented on the Company’s consolidated statements of cash flows and that would provide an indication of the Company’s ability to generate cash flows from its mineral projects. Return on Equity is defined as Earnings from Continuing Operations divided by the average Total Equity for the current and previous year. “Mining cost per tonne of ore” and “Cost per tonne of ore” are non-GAAP performance measures that could provide an indication of the mining and processing efficiency and effectiveness of the mine. These measures are calculated by dividing the relevant mining and processing costs and total costs by the tonnes of ore processed in the period. “Cost per tonne of ore” is usually affected by operating efficiencies and waste-to-ore ratios in the period. “Cash operating costs per ounce”, “total cash costs per ounce” and “all-in sustaining costs per ounce” as used in this analysis are non-GAAP terms typically used by gold mining companies to assess the level of gross margin available to the Company by subtracting these costs from the unit price realized during the period. These non-GAAP terms are also used to assess the ability of a mining company to generate cash flow from operations. There may be some variation in the method of computation of these metrics as determined by the Company compared with other mining companies. In this context, “cash operating costs per ounce” reflects the cash operating costs allocated from in-process and dore inventory associated with ounces of gold sold in the period. “Cash operating costs per ounce” may vary from one period to another due to operating efficiencies, waste-to-ore ratios, grade of ore processed and gold recovery rates in the period. “Total cash costs per ounce” includes “cash operating costs per ounce” plus applicable royalties. Cash operating costs per ounce and total cash costs per ounce are exclusive of exploration costs. “All-in sustaining costs per ounce” include total cash costs, exploration, corporate and administrative, share based compensation and sustaining capital costs. Non-GAAP and additional GAAP measures do not have a standardized meaning prescribed under IFRS and therefore may not be comparable to similar measures presented by other companies. For a reconciliation of non-GAAP and GAAP measures, please refer to Alamos’ Managements’ Discussion and Analysis as presented on SEDAR and the Company’s website.

Technical Information

Except as otherwise noted herein, Chris Bostwick, FAusIMM, Alamos Gold’s Vice President, Technical Services, has reviewed and approved the scientific and technical information contained in this website. Chris Bostwick is a Qualified Person within the meaning of Canadian Securities Administrator’s National Instrument 43-101. For more information, please refer to the Alamos Gold Inc. and AuRico Gold Inc. 2014 Annual Information Forms and the technical reports referenced therein and in this website, available on SEDAR (