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Mexico
San Dimas Mine

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 Location:
107 km NE from Mazatlan, Durango, Mexico

  Address:
Domicilio conocido s/n, Tayoltita Centro
San Dimas
Durango, Mexico
34690
Phone  ...  Subscription required
Fax01-(669)-915-9834
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Fleet
  • Personnel
  • Filings & News

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Overview

StageProduction
Mine TypeUnderground
Commodities
  • Silver
  • Gold
Mining Method
  • Mechanized Cut & Fill
  • Longhole stoping
  • Dry waste backfill
Processing
  • Smelting
  • Filter press plant
  • Agitated tank (VAT) leaching
  • Counter current decantation (CCD)
  • Merrill–Crowe
  • Cyanide (reagent)
Mine Life2025
Latest NewsFirst Majestic Files Updated Technical Reports, 2020 Mineral Reserve and Mineral Resource Estimates & Appoints New Director     March 31, 2021


Owners

Source: p. 15,30
CompanyInterestOwnership
First Majestic Silver Corp. 100 % Indirect
First Majestic acquired the San Dimas mine in May 2018 with the acquisition of Primero Mining Corp.

The San Dimas Silver Mine is owned and operated by the First Majestic Silver Corp. wholly-owned indirect subsidiary, Primero Empresa Minera S.A. de C.V.

Deposit Type

  • Epithermal
  • Vein / narrow vein


Summary:

The vein-hosted mineral deposits within the San Dimas Mine district are considered to be examples of silver- and gold-bearing epithermal quartz veins that formed in a low-sulphidation setting. Epithermal veins are typically localized along structures but may also form in permeable lithologies. Upward-flaring ore zones centred on structurally controlled hydrothermal conduits are typical. Large to small veins and stockworks are common. Vein systems can be laterally extensive, but the associated ore shoots have relatively restricted vertical extent. High-grade ores are commonly form within dilational faults zones near flexures and fault splays. Textures typical of low-sulphidation quartz vein deposits include open-space filling, symmetrical and other layering, crustification, comb structure, colloform banding and complex brecciation.

Within the San Dimas district, the mineralization is typical of epithermal vein structures with banded and drusy textures. Epithermal-style veins occupy east–west-trending fractures, except in the southern part of the Tayoltita Block where they strike mainly northeast, and in the Santa Rita area where they strike north–northwest.

The silver- and gold-rich quartz veins formed in two different phases. The east–west striking veins developed first, followed by a second system of north–northeast-striking veins. Veins pinch and swell and commonly exhibit bifurcation, horse-tailing, and sigmoidal structures. The veins have been followed underground from a few metres in strike-length to more than 1,500 m. One of these veins, the Jessica Vein, extends for more than 1,000 m in the Central Block.

Three major stages of mineralization have been recognized in the district: (1) early stage; (2) ore forming stage; and (3) late-stage quartz. The minerals characteristic of the ore-forming stage consist of white, to light grey, medium to coarse grained crystalline quartz with intergrowths of base metal sulphides (sphalerite, chalcopyrite and galena) as well as pyrite, argentite, polybasite, stromeyerite, native silver and electrum. The veins are formed by filling previous fractures and typical textures observed include crustification, comb structure, colloform banding and brecciation.


Mining Methods

  • Mechanized Cut & Fill
  • Longhole stoping
  • Dry waste backfill


Summary:

The San Dimas mine includes five main underground gold and silver mining areas: West Block (San Antonio mine), Sinaloa Graben Block (Graben Block), Central Block, Tayoltita Block, and the Arana Hanging-wall Block (Santa Rita mine). In 2020, 68% of ROM production came from the Central Block, 29% from the Sinaloa Graben and 3% from the Tayoltita Block and other areas.

Access to the mining areas is achieved by adits and internal ramps. The Central Block and Sinaloa Graben rely solely on truck haulage, whereas Tayoltita ROM material is transported to the surface stockpile via rail. Main accesses are typically driven at 5 m wide by 5 m high, with accesses to the stopes at 3 m wide by 3 m high. Typical rail haulageway dimensions are 3.5 m wide by 3.5 m high.

Internal ramps connect stopes from both the hanging wall and foot wall, and often, when two or more veins are in close proximity, single ramps can provide access to multiple veins.

The predominant mining methods at the San Dimas mine are mechanized cut-and-fill and longhole mining. Longhole mining was introduced in 2012 and is becoming increasingly important.

Cut-and-fill mining is carried out using jumbo or jackleg drills and load-haul-dump (LHD) machines. Minimum mining widths of 2.5 m and 0.8 m for jumbo and jackleg mining, respectively, may be attainable. Waste rock is used as fill material and provides both wall support and a working base from which to take subsequent cuts after the initial sill cut.

Typically, an initial 3.5 m high sill cut is taken followed by a second 3.0 m cut. Waste rock is then used to fill the void to about 1.0 m from the back, so as to form the working floor for the next cut. The next 3.0 m cut is then breasted down on top of the fill. When this mineralized material is mucked out, filling occurs again to within about 1.0 m of the back. The process is repeated until within about 4.0 m of the next sill cut. Sills beneath waste fill are mined using uppers. The general mining recovery factor is about 95%, and that for sill mining is about 75%.

Longhole mining consists of drilling production holes in the pillar between two mineralized drifts. A minimum mining width of 1.2 m is envisaged for the method. A drop raise or an inverse raise is drilled and blasted at the extremity of the mining block. The length of the block is determined relative to the geotechnical condition of the exposed walls. Stopes can be mined either with upholes or downholes, with respective maximum heights of 12 m and 15 m. The longhole mining method offers increased productivity, lower unit operating costs, and reduced waste dilution in veins of consistent geometry.

Twelve-metre long upholes are drilled from the lower drift. In this example, the blast holes are stopped 4 m from breakthrough into the upper drift to maintain a sill pillar. Where possible, holes are drilled along the contact of the vein, and typical overbreak on the hanging-wall and footwall is approximately 0.3 m. San Dimas has regularly mined veins less than 1 m in width with success using this method.

Ore from the three mine areas, Central Block, West Block, and Sinaloa Graben, is hauled to the mill site via three main tunnels know as the San Luis, San Fernando, and San Francisco tunnels. The mine is setup with a series of ore passes that connect the stopes areas to the haulage levels for the material to flow and to be loaded and hauled to surface and the plant stockpiles. From there, the ROM material is hauled to the mill site and dumped in the stockpile patios or directly into the crusher. The ROM material from the Tayoltita mine sector is transported by rail to the mill.

Ore is hauled from the underground mine to the surface by means of 14 m3 conventional trucks. Most truck haulage at San Dimas is carried out by contractors, however First Majestic has 12 trucks
used for material transfers inside the mine.

The waste material from the main underground infrastructure development is used as backfill for longhole and cut-and-fill stopes. The rock size distribution is adequate to stabilize the cavities and no cement is needed. The back-filling process is carried out with the same equipment used for mucking and hauling.


Crushing and Grinding
Flow Sheet: Source
Crusher / Mill TypeModelSizePowerQuantity
Jaw crusher 20" x 36" 1
Cone crusher ....................... Subscription required 7' 2
Ball mill 12' x 14' 1500 HP 3

Summary:

Crushing
The crushing plant is divided into two parts: primary crushing and secondary crushing. The coarseore bin has a lower discharge chute that discharges into a vibrating feeder. The -12” + 4” material is fed into a 20” x 36” primary jaw crusher and reduced to a minus 3” to 3-½”. This product is transported by a belt conveyor to a 450 t capacity secondary bin, which subsequently feeds an 8’ x 16’ double-deck vibrating screen.

The upper section has 1” x 1” openings, while the lower section has ½” x ½” openings. The underflow of the screen contains material from 90–95% minus 5/16” (8 mm), as well as an average of 70% minus ¼” (6.4 mm).

The upper discharge of the vibrating screen flows into one of two 7’ Symons short head secondary crushers that reduces the size to minus 5/16”. There are two secondary crushers, one working and the other on standby. The secondary crusher product becomes the circulating load which returns to the screen feed.

The lower discharge of the vibrating screen (underflow) is transported through a belt conveyor and a pipe conveyor and unloaded into two ore bins (number 3 & 4), which have a capacity of 1,300 t each.

The fine mineralized material is considered 90–95% minus 5/16” with average moisture content of 3–4%. The overall crushing plant capacity is 145 t/hr.

Grinding
The grinding section consists of three ball mills circuit. The three mills have the same dimensions: 12’ diameter x 14’ long equipped with 1,500 HP drives and D-20” gMax Krebs cyclones. Every ball mill is equipped with a cyclone classification system and a pair of pumps (one in operation the second on stand-by). The mills only use 3” diameter balls.

The crushed ore from bin #3 feeds ball mill #1, while bin #2 feeds ball mills #2 and #3.

The reagents added in the mills are as follows:
• Cyanide: grinding is carried out by adding semi-pregnant solution, which has a cyanide concentration of 1,000 ppm;
• Lime: added only in ball mills #1 and #2 in dry form. Lime consumption is 0.7 kg/t;
• Litharge (lead oxide) added in all three ball mills (35 g/t).

The average pulp densities that are handled at each point of the circuits are as follows:
• Ball mill discharge 1.85 kg/L (75% solids);
• Cyclone underflow 1.90 kg/L (77% solids);
• Cyclone overflow 1.20 kg/L (27% solids).
The final ground product is approximately 70% minus 200 mesh, equivalent to a P80 of 90 µm. The product of the three grinding circuits is pumped to the two primary thickeners (hi-capacity) with dimensions of 55’ x 12’ and 48’ x 12’.


Processing

  • Smelting
  • Filter press plant
  • Agitated tank (VAT) leaching
  • Counter current decantation (CCD)
  • Merrill–Crowe
  • Cyanide (reagent)

Flow Sheet: Subscription required

Summary:

The processing plant at the San Dimas has been successfully operating for several years and continuously achieved high levels of recoveries for silver and gold. The process is based on cyanide tank leaching and Merrill-Crowe precipitation of ground plant-feed to produce silver–gold doré bars. The installed plant capacity is for 3,000 tpd. However, the current throughput levels are around 2,000 tpd. The average feed contains head grades in the order of 300 g/t Ag and 3.6 g/t Au.

The plant consists of the following operating units:
• Crushing – a two-stage crushing circuit with a primary jaw crusher followed by two cone crushers, one in operation and one in standby, in closed circuit with dry vibrating screens;
• Grinding – three ball mills, each paired with hydrocyclones in closed circuit working in parallel;
• Cyanide leaching – plant-feed is leached with cyanide in a series of agitated tanks;
• Counter current decantation (CCD) – two CCD thickeners worki ........

Recoveries & Grades:

CommodityParameter2021202020192018201720162015
Silver Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required95949695
Silver Head Grade, g/t  ......  Subscription required  ......  Subscription required  ......  Subscription required274296228274
Gold Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required97979897
Gold Head Grade, g/t  ......  Subscription required  ......  Subscription required  ......  Subscription required44.363.944.9

Production:

CommodityProductUnits2022202120202019201820172016
Silver Metal in doré koz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required  ......  Subscription required3,6223,9605,320
Gold Metal in doré koz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Silver Equivalent Metal in doré koz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Silver Equivalent Payable metal koz  ......  Subscription required  ......  Subscription required  ......  Subscription required
Silver Payable metal koz  ......  Subscription required  ......  Subscription required3,618
Gold Equivalent Metal in doré oz  ......  Subscription required  ......  Subscription required
^ Guidance / Forecast.
Subscription required - Subscription is required.

Operational Metrics:

Metrics202120202019201820172016
Tonnes milled  ......  Subscription required  ......  Subscription required691,576 t435,289 t444,711 t759,087 t
Daily milling capacity  ......  Subscription required  ......  Subscription required2,500 t2,500 t
Annual milling rate  ......  Subscription required  ......  Subscription required
Ore tonnes mined  ......  Subscription required  ......  Subscription required437,918 t762,167 t
Daily milling rate  ......  Subscription required  ......  Subscription required1,555 t2,074 t
Subscription required - Subscription is required.

Reserves at December 31, 2021:
Cut-off grade considered to constraint resources assuming an underground operation was 165 g/t Ag-Eq.

CategoryTonnage CommodityGradeContained Metal
Proven 2,328 kt Silver 348 g/t 26,050 koz
Proven 2,328 kt Gold 4.42 g/t 330.8 koz
Proven 2,328 kt Silver Equivalent 697 g/t 52,190 koz
Probable 1,506 kt Silver 265 g/t 12,820 koz
Probable 1,506 kt Gold 3.02 g/t 146.4 koz
Probable 1,506 kt Silver Equivalent 504 g/t 24,390 koz
Proven & Probable 3,834 kt Silver 315 g/t 38,870 koz
Proven & Probable 3,834 kt Gold 3.87 g/t 477.2 koz
Proven & Probable 3,834 kt Silver Equivalent 621 g/t 76,580 koz
Measured 2,546 kt Silver 474 g/t 38,780 koz
Measured 2,546 kt Gold 6.15 g/t 503 koz
Measured 2,546 kt Silver Equivalent 924 g/t 75,640 koz
Indicated 1,906 kt Silver 336 g/t 20,580 koz
Indicated 1,906 kt Gold 3.83 g/t 235 koz
Indicated 1,906 kt Silver Equivalent 616 g/t 37,770 koz
Measured & Indicated 4,452 kt Silver 415 g/t 59,360 koz
Measured & Indicated 4,452 kt Gold 5.15 g/t 737 koz
Measured & Indicated 4,452 kt Silver Equivalent 792 g/t 113,410 koz
Inferred 4,073 kt Silver 310 g/t 40,660 koz
Inferred 4,073 kt Gold 3.54 g/t 463 koz
Inferred 4,073 kt Silver Equivalent 570 g/t 74,630 koz

Commodity Production Costs:

CommodityUnits2021202020192018201720162015
Total cash costs Silver Equivalent USD  ......  Subscription required  ......  Subscription required  ......  Subscription required
Total cash costs Silver USD  ......  Subscription required  ......  Subscription required 14.6 / oz
Total cash costs Gold Equivalent USD 939 / oz 856 / oz 559 / oz
Total cash costs Silver USD  ......  Subscription required†  ......  Subscription required† 0.11 / oz†
Total cash costs Gold USD 867 / oz† 774 / oz† 409 / oz†
All-in sustaining costs (AISC) Silver Equivalent USD  ......  Subscription required  ......  Subscription required  ......  Subscription required
All-in sustaining costs (AISC) Silver USD  ......  Subscription required†  ......  Subscription required† 5.92 / oz†
All-in sustaining costs (AISC) Gold USD 1,216 / oz† 1,117 / oz† 680 / oz†
^ Guidance / Forecast.
† Net of By-Product.
Subscription required - Subscription is required.

Operating Costs:

Units2021202020192018
Total operating costs ($/t milled) USD 142127.91131.9117.46

Financials:

Units2021202020192018201720162015
Sustaining costs M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required16.8   2.5   11.4   16.9  
Capital expenditures M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required20.5   21.8   36.2   56.5  
Revenue M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required102.5   91.8   147.6   213.2  
Operating Income M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required22.7   -312.8   -120.5   48.8  
After-tax Income M USD -309   -102   12  
EBIT M USD -313.9   -122   44.6  
Subscription required - Subscription is required


Heavy Mobile Equipment as of December 31, 2020:
HME TypeSizeQuantity
Drill (long hole) 20 m ....................... Subscription required
Jumbo 16 ft ....................... Subscription required
Jumbo 12 ft ....................... Subscription required
Jumbo 14 ft ....................... Subscription required
Load-Haul-Dump (LHD) 1.5 cu. yd ....................... Subscription required
Load-Haul-Dump (LHD) 2 cu. yd ....................... Subscription required
Load-Haul-Dump (LHD) 3 cu. yd ....................... Subscription required
Load-Haul-Dump (LHD) 4 cu. yd ....................... Subscription required
Load-Haul-Dump (LHD) 6 cu. yd ....................... Subscription required
Load-Haul-Dump (LHD) 8 cu. yd ....................... Subscription required
Raise boring rig 6 ft ....................... Subscription required
Raise boring rig 8 ft ....................... Subscription required
Truck (haul) 10 tons ....................... Subscription required
Truck (haul) 15 tons ....................... Subscription required
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Apr 18, 2022
....................... Subscription required ....................... Subscription required Subscription required Apr 18, 2022
....................... Subscription required ....................... Subscription required Subscription required Apr 18, 2022
....................... Subscription required ....................... Subscription required Subscription required Apr 18, 2022
Subscription required - Subscription is required.

Staff:

EmployeesContractorsTotal WorkforceYear
Subscription required Subscription required Subscription required 2020
Subscription required Subscription required 2017
Subscription required Subscription required 2014

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
Annual Information Form 2018
Annual Report 2018
Annual Information Form 2017
Form 20-F 2017
Management Discussion & Analysis 2017
Press Release 2017
Press Release 2016
Annual Report 2014
Technical Report 2014
Annual Information Form 2012
Subscription required - Subscription is required.

News:

NewsDate
First Majestic Files Updated Technical Reports, 2020 Mineral Reserve and Mineral Resource Estimates & Appoints New Director March 31, 2021
First Majestic Reports First Quarter Financial Results; Temporarily Postpones the Sale of Silver and Gold Due to COVID-19; Announces Operational Restart Procedures May 14, 2020
First Majestic Updates 2019 Mineral Reserve and Resource Estimates March 30, 2020
First Majestic Completes Acquisition of Primero Mining May 11, 2018

Aerial view:

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