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Mexico
San Francisco Mine

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 Location:
142 km N from Hermosillo, Sonora, Mexico

  Regional Office:
Blvd. Paseo de las Quintas 123, local 101
Hermosillo
Sonora, Mexico
CP 83247
Phone  ...  Subscription required
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Fleet
  • Personnel
  • Filings & News

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Overview

StageProduction
Mine TypeOpen Pit
Commodities
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
Processing
  • Heap leach
  • Carbon in column (CIC)
  • Elution
  • Carbon adsorption-desorption-recovery (ADR)
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)
Mine Life6.5 years (as of Jan 1, 2018)
Production from the La Chicharra deposit recommenced in June, 2020. The San Francisco and La Chicharra pits are planned to be mined at the same time. Magna is also processing the remainder of Alio’s low-grade stockpile.
Latest NewsMagna Gold Corp. Announces Pre-Feasibility Study on the San Francisco Mine     September 17, 2020


Owners & OPERATOR

Source:
CompanyInterestOwnership
Peal Mexico SA de CV (operator)
Magna Gold Corp. 100 % Indirect
All mining activities were conducted by the contractor, Peal Mexico, S.A. de C.V., of Navojoa, Mexico.
[https://minedocs.com/20/San_Francisco_TR_06012020.pdf P.228]

Deposit Type

  • Vein / narrow vein
  • Orogenic


Summary:

At the San Francisco Project, Alio is targeting large volume, low grade disseminated gold deposits contained within leucocratic granite, granite-gneiss and gneiss and schist horizons. Leucocratic granite and gneiss are the main rocks hosting the gold mineralization.

The gold mineralization occurs in a series of west-northwest to east-northeast trending quartztourmaline veins and veinlets that lie sub-parallel to the local lithology and foliation trends, dipping to the southwest, within the more brittle rocks such as the leucocratic granite and more felsic lithologies within the Precambrian sequence. Extensive studies of the veins and alteration describe the mineralization as mesothermal/orogenic in style, but with a potential link to magmatic fluids and an intrusive source (Calmus et al., 1992; Luna and Gastelum, 1992; Perez Segura, 1992; Perezsegura et al., 1996; Perez Segura, 2008; Albinson, 1997; Poulsen and Mortensen, 2008).

At the San Francisco Project, gold occurs principally as free gold and as electrum occasionally. Gold is found, in decreasing abundance, with goethite after pyrite, with pyrite and, to a much lesser extent, with quartz, galena and petzite (Ag3AuTe2). Although it is clear that the gold was deposited at the same time as the sulphides, the paragenetic relationships are not well understood. There is the possibility that some secondary remobilization may have occurred as evidenced by minor amounts of gold occurring in irregular forms along with or on top of drusy quartz (Prenn, 1995).

The gold occurs in a granitic gneiss and the presence of pyrite (or goethite after pyrite) may be an indication of gold. Stockwork quartz veinlets, some with tourmaline, also exist in the mineralized zone. However, the presence of quartz, even with tourmaline, is not necessarily an indication of the presence of gold. Quartz veinlets with tourmaline but without gold mineralization were found hundreds of metres away from the San Francisco deposit. Alvarez (in Prenn, 1995) suggested that some tourmaline was part of the mineralizing system, but could be distinguished from the tourmaline found elsewhere.

The relationship between the quartz and tourmaline at the Project is not well understood, though at least one event is closely related to the gold mineralization. Calmus (1992) and Perez (1992) described the gold as being in quartz, acicular tourmaline, and albite veins and breccias. It was noted (Perez, 1992) that two types of tourmaline exist: schorl and dravite, but these are difficult to distinguish. There is some suggestion that a more greenish tourmaline is associated with the San Francisco zone while the black tourmaline (schorl) is generally barren of gold. If this can be verified, it could become a valuable exploration tool for the region. Horner (in Prenn, 1995) also noted the possibility of two or more types of tourmaline in the cobbles sampled in the stream beds. Horner believes that only one set of the tourmaline veins is associated with the gold and suggests that bismuth is also associated with one tourmaline quartz vein event.

Other metallic minerals associated with the deposit include trace to small amounts of chalcopyrite, galena, sphalerite, covelite, bornite, argentite-acanthite and pyrrhotite. Trace amounts of molybdenite and wulfenite have also been reported. Metal mineralization is low, with copper reaching into the hundreds of ppm, arsenic reaching about 100 ppm, and antimony rarely over 10 ppm. Petzite was recognized but tellurium values rarely reached 10 ppm. The mineral relationships, the possibility of associated tourmaline, and the style of mineralization suggest that the San Francisco deposit might be of mesothermal origin (see Prenn, 1995 for discussion). Others have suggested the same genesis based on these and other factors, including fluid inclusion studies (in Prenn, 1995).

The San Francisco deposits are roughly tabular with multiple phases of gold mineralization. The deposits strike 60° west to 65° west, dip to the northeast, range in thickness from 4 to 50 m, extend over 1,500 m along strike and are open ended. The San Francisco deposits consisted of the El Manto, the San Francisco, the En Medio and the El Polvorin deposits. All of these deposits were later incorporated into the main San Francisco pit. The El Manto deposit (north pit), to the north of the San Francisco (main pit), is tabular, strikes 65° west, dips relatively shallowly to the northeast, and ranges in thickness from 5 to 35 m. The En Medio (in the main pit north of San Francisco) strikes 60° west, dips to the northeast and varies in thickness from 4 to 20 m. The El Polvorin (west pit) is a northwest extension of the San Francisco mineralization which strikes 65° west, dips moderately to the northeast and ranges in thickness from 4 to 20 m.

Alteration related to the mineralization consists of negligible to locally intense sericitization, course-grained pyritization and rare local silicification. This alteration forms a halo extending a few metres from the mineral deposits, but may also be absent. Supergene alteration consisting of oxidation of pyrite to goethite is common. Additionally, there is supergene alteration of feldspar to kaolin and sericite.

Analysis by Geomaque of 110 samples in seven mineralized zones showed a silver/gold ratio of less than 1 to 10, with very low values of zinc, copper, molybdenum, bismuth, antimony and mercury. Lead is occasionally high, but not above 1% while gold shows a good correlation locally with arsenic and lead. However, none of the other elements is a good indicator for gold.


Mining Methods

  • Truck & Shovel / Loader


Summary:

The San Francisco and La Chicharra pits will be mined at the same time. The La Chicharra pit, previously mined by Geomaque, is located 1,000 m west of the San Francisco pit.

All mining activities are being carried out by the contractor, Peal Mexico, S.A. de C.V., of Navojoa, Mexico. The contractor is obliged to supply and maintain the appropriate principal and auxiliary mining equipment and personnel required to produce the tonnage mandated by Alio, in accordance with the mining plan.

In addition to the open pit, Alio previously conducted an investigation into whether or not it is economical to conduct limited underground mining beneath the southern pit wall of the San Francisco pit. In 2015, Alio conducted limited underground drifting to expose the mineralized lenses outlined in preliminary drilling. In September, 2015, Alio ceased the underground drifting after exposing the mineralization along two lenses. Alio was contemplating doing further drilling to define the extent of the mineralization exposed in the workings and also to assist it in deciding the best underground mining method, should it proceed with mining these lenses.

In the latest open pit design, the mineral resources previously identified to be mineable via underground mining methods will be recovered by conducting a pushback of the pit all in the southern direction towards the waste dumps. This pushback will constitute a fifth phase of mining at the San Francisco pit.


Crushing and Grinding


Processing

  • Heap leach
  • Carbon in column (CIC)
  • Elution
  • Carbon adsorption-desorption-recovery (ADR)
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)

Flow Sheet: Subscription required

Summary:

Ore extracted from the pit is transported in 100 t capacity haulage trucks and fed directly into the gyratory primary crusher with dimensions of 42 inch x 65 inch. The primary crusher has a nominal capacity of 900 t/h. The crushed product is then transported on conveyor belts to a coarse ore stockpile with a capacity of 6,000 t.

Two feeders beneath the coarse ore stockpile deliver the material to a conveyor belt for transport to the secondary crushing circuit. The ore is screened at 12.5 mm (½ inch). Screen undersize reports to the final product, while screen oversize is fed to two secondary crushers.

Product from the secondary crushers is transported on conveyor belts to the tertiary crushing circuit, which comprises three parallel tertiary crushers operating in closed circuit with screens. The minus 12.5 mm undersize from the screens is delivered to the leach pad. This crushing circuit had a nominal capacity to deliver 16,000 t/d of crushed material to the leach ........

Recoveries & Grades:

CommodityParameter201920182017201620152014
Gold Head Grade, g/t  ......  Subscription required  ......  Subscription required0.450.580.540.64

Production:

CommodityUnits201920182017201620152014
Gold oz  ......  Subscription required53,99083,558100,32293,353120,023
Silver oz  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
All production numbers are expressed as metal in doré.
Subscription required - Subscription is required.

Operational Metrics:

Metrics201920182017201620152014
Tonnes processed  ......  Subscription required  ......  Subscription required7,537 kt7,652,642 t8,448,731 t8,622,579 t
Daily processing rate  ......  Subscription required  ......  Subscription required20,649 t20,909 t23,147 t23,624 t
Total tonnes mined  ......  Subscription required  ......  Subscription required25,956 kt22,353,870 t34,887,513 t32,752,482 t
Ore tonnes mined  ......  Subscription required  ......  Subscription required6,997 kt7,457,484 t7,880,292 t8,796,579 t
Waste  ......  Subscription required  ......  Subscription required18,960 kt14,896,386 t27,007,221 t23,955,903 t
Stripping / waste ratio  ......  Subscription required  ......  Subscription required2.71 2 3.43 2.72
Daily mining rate  ......  Subscription required  ......  Subscription required71,113 t61,076 t95,582 t89,733 t
Subscription required - Subscription is required.

Reserves at July 1, 2018:
The Mineral Resources as at 31th December 2019 at San Francisco mine are unchanged from July 1, 2018

CategoryOreTypeTonnage CommodityGradeContained Metal
Proven Stockpiles 7,199,000 t Gold 0.26 g/t 60,200 oz
Proven In-Situ (OP) 23,085,826 t Gold 0.489 g/t 363,230 oz
Probable In-Situ (OP) 25,195,005 t Gold 0.532 g/t 431,043 oz
Proven & Probable In-Situ (OP) 48,280,831 t Gold 0.512 g/t 794,272 oz
Measured In-Situ (OP) 39,715,871 t Gold 0.547 g/t 698,574 oz
Indicated In-Situ (OP) 44,505,325 t Gold 0.549 g/t 785,621 oz
Measured & Indicated In-Situ (OP) 84,221,196 t Gold 0.548 g/t 1,484,197 oz
Inferred In-Situ (OP) 1,947,846 t Gold 0.52 g/t 32,594 oz

Commodity Production Costs:

CommodityUnits201920182017201620152014
Credits (by-product) Gold USD -8 / oz -10 / oz -8 / oz -13 / oz
Cash costs (sold) Gold USD 839 / oz 744 / oz 1,025 / oz 803 / oz
Cash costs (sold) Gold USD  ......  Subscription required† 1,042 / oz† 831 / oz† 734 / oz† 1,017 / oz† 790 / oz†
All-in sustaining costs (sold) Gold USD  ......  Subscription required† 1,258 / oz† 1,034 / oz† 853 / oz† 1,144 / oz† 925 / oz†
† Net of By-Product.
Subscription required - Subscription is required.

Operating Costs:

Units201920182017
OP mining costs ($/t mined) USD 1.142.022
Processing costs ($/t milled) USD  ......  Subscription required  ......  Subscription required  ......  Subscription required
Total operating costs ($/t milled) USD  ......  Subscription required  ......  Subscription required
Subscription required - Subscription is required.

Financials:

Units201920182017201620152014
Capital expenditures M USD  ......  Subscription required11.3  20.9   5.65  
Sustaining costs M USD 8.73   4.3   1.31   2.24  
Revenue M USD  ......  Subscription required67.2  105.16   123.87   109.19   154.07  
Operating Income M USD  ......  Subscription required-10.49  28.7   56.5   -241.78   22.2  
After-tax Income M USD -190.31   9.19  
EBIT M USD -240.57   20  
Operating Cash Flow M USD 13.1   34.1   13.3   33.1  
Subscription required - Subscription is required


Heavy Mobile Equipment as of April 1, 2017:
HME TypeModelQuantityLeased or
Contractor
Dozer ....................... Subscription required 1 Leased
Dozer ....................... Subscription required 3 Leased
Dozer ....................... Subscription required 2 Leased
Drill ....................... Subscription required 2 Leased
Drill ....................... Subscription required 7 Leased
Drill ....................... Subscription required 1 Leased
Drill ....................... Subscription required 1 Leased
Grader ....................... Subscription required 2 Leased
Loader ....................... Subscription required 2 Leased
Shovel ....................... Subscription required 3 Leased
Shovel ....................... Subscription required 1 Leased
Truck (haul) ....................... Subscription required 14 Leased
Truck (haul) ....................... Subscription required 9 Leased
Truck (water) ....................... Subscription required 3 Leased
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Jul 10, 2020
Subscription required - Subscription is required.

Staff:

EmployeesContractorsTotal WorkforceYear
Subscription required 2019
Subscription required Subscription required 2018
Subscription required Subscription required 2017
Subscription required Subscription required 2016

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
Annual Information Form 2018
Corporate Presentation 2018
Financial Review 2018
Management Discussion & Analysis 2018
Press Release 2018
Annual Information Form 2017
Corporate Presentation 2017
Financial Review 2017
Management Discussion & Analysis 2017
Press Release 2017
Technical Report 2017
Annual Information Form 2016
Financial Review 2016
Form 40-F 2016
Management Discussion & Analysis 2016
Form 40-F 2015
Technical Report 2015
Technical Report 2013
Subscription required - Subscription is required.

News:

NewsDate
Magna Gold Corp. Announces Pre-Feasibility Study on the San Francisco Mine September 17, 2020
Alio Gold Completes Sale of San Francisco Mine May 6, 2020
Magna Gold Corp. Provides Update on Acquisition of the San Francisco Mine and Private Placement April 24, 2020
Alio Gold Announces Sale of San Francisco Mine March 6, 2020
Magna Gold Corp. Announces acquisition of the San Francisco Mine and Private Placement March 6, 2020

Aerial view:

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