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United States
Mesquite Mine

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 Location:
50 km NW from Yuma, California, United States

  Address:
6502 E. U S Highway 78
Brawley
California, United States
92227
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WebsiteWeb
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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
Mining Method
  • Truck & Shovel / Loader
Processing
  • ROM/dump leach
  • Carbon in column (CIC)
  • AARL elution
  • Carbon adsorption-desorption-recovery (ADR)
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)
Mine Life3.25 years (as of Jan 1, 2019)
Latest NewsEquinox Gold Increases Mesquite Reserves by 28% and Measured & Indicated Resources by 94%     October 8, 2020


Owners

 
CompanyInterestOwnership
Western Mesquite Mines Inc. 100 % Direct
Equinox Gold  Corp. 100 % Indirect

Deposit Type

  • Epithermal
  • Vein / narrow vein


Summary:

The gold mineralization at Mesquite Mine was deposited in an epithermal setting, within 500 to 1,000 ft of the surface. The majority of the economically attractive mineralization is found in the biotite gneiss and hornblende-biotite gneiss, while the mafic gneiss and intrusive rocks are generally less mineralized. Gold mineralization is found both disseminated and vein hosted within these units. The majority of the veining is controlled by faults and fault junctions, which have moderate to steep dips.

The gold mineralization dominantly occurs in two types:

- pods of mineralization limited in lateral and vertical extent at fault intersections

- trends of mineralization along faults.

The principal types of mineralization defined at Mesquite are as follows:
• Early epidote - quartz veinlets overprinted by chlorite veinlets;
• Two-stage siliceous matrix breccia (SMBX) developed along faults planes with quartzadularia matrix ± pyrite;
• Quartz ± adularia ± pyrite ± electrum veinlets with sericite halos;
• Ankerite ± Dolomite ± pyrite veinlets;
• Bleached zones on fault planes with green sericite ± pyrite;

Gold occurs at Mesquite as both submicron disseminated and coarse gold. All documented gold occurrences are native gold, and classification has been based on silver content and grain size. A silver-free native gold is the most common type in the oxidized zone. It occurs in particles less than five microns, although clusters up to 100 µ are common in fault zones. Gold grains are subhedral to anhedral in shape, with anhedral morphology predominating. In general, the grains are characterized by irregular, ragged boundaries and equant to elongate shape. Gold within the oxide portion of the deposit is commonly associated with goethite pseudomorphs after pyrite and mica minerals. Later stage gold, less than five microns, is found along the cleavages of the micas.

A second type of gold is the silver-bearing (5% to 20%) coarse (10 µ to 600 µ) gold. Its average size is 30 µm to 50 µm and it is typically found in the unoxidized zone, and only occasionally in the oxidized zone. Grains have octahedral morphology, with cuspate to sharp boundaries. Gold specimens are usually bright yellow electrum, with minor inclusions of galena and pyrite. Silver-bearing gold is associated with quartz-adularia pyrite veins containing arsenopyrite, magnetite, and chalcopyrite.

Visible gold has been identified throughout Mesquite. Small flakes, less than 50 µm, of free “flour” gold have been found within the oxidized gouge and clay fault zones. The flour gold is thought to be a result of remobilization during oxidation and is supergene in nature. Gold is typically associated with titanium oxides (rutile) and hematite. These zones are limited in extent (one inch to three feet wide, with three feet to 50 ft of strike length), but can be extremely high grade. Selective sampling indicates typical gold values of 1.0 opt to 2.0 opt Au, with a high of 35.9 opt Au recorded in Big Chief.

Coarse-grained hypogene gold has also been noted with more frequency and larger size in the unoxidized portion of the deposits. Recent test work on non-oxidized ore indicates that 65% to 78% of the gold is liberated free milling gold, 13% is associated with refractory sulphide minerals, and the remainder is associated with iron oxides and carbonates. Grain size ranges from 10 µm to 600 µm, with no textural indications of re-mobilization. Coarse gold generally occurs as electrum within quartz veins (occluded and void fill), while the refractory portion is found within overgrowth rims of arsenopyrite, chalcopyrite, and pyrite.


Mining Methods

  • Truck & Shovel / Loader


Summary:

Mining is performed using a conventional ruck/shovel open pit mining method. Operations include drilling, blasting, loading, and hauling. Run-of-mine ore is hauled directly to the leach pad to the south for processing. Waste mining uses the same equipment fleet used to produce ore.


Crushing and Grinding


Processing

  • ROM/dump leach
  • Carbon in column (CIC)
  • AARL elution
  • Carbon adsorption-desorption-recovery (ADR)
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)

Flow Sheet: Subscription required

Summary:

The Mesquite Mine is an operating open pit mine with ore processing by heap leaching using a carbon-in-column (CIC) circuit to recover gold.

The processing facilities include the following operations:
• Heap leaching
• Carbon adsorption
• Desorption and gold recovery
• Reagents and utilities
• Water services.

Originally the ore was crushed, however since the operation was re-started in 2007, on run-ofmine (ROM) ore is leached. ROM ore, with lime added for pH control, is trucked to the heap leach pad. The ore is stacked to a height of 20 ft. The ultimate pad height has been increased from 200 ft to 300 ft.

Dilute sodium cyanide solution is pumped from either the barren or the intermediate solution ponds and distributed to the surface of the leach pad with drip emitters. The solution then percolates through the pad extracting the gold. The gold bearing pregnant solution is collected in a series of flume boxes, with the option to ........

Recoveries & Grades:

CommodityParameter20192018201720162015201420132012
Gold Head Grade, g/t 0.320.340.320.380.340.40.370.46

Production:

CommodityUnits201920182017201620152014
Gold oz  ......  Subscription required  ......  Subscription required168,889111,123134,868106,670
All production numbers are expressed as metal in doré.
Subscription required - Subscription is required.

Operational Metrics:

Metrics20192017201620152014
Ore tonnes mined  ......  Subscription required  ......  Subscription required18,969 kt19,987 kt13,550 kt
Waste  ......  Subscription required  ......  Subscription required39,782 kt38,791 kt37,107 kt
Stripping / waste ratio  ......  Subscription required  ......  Subscription required2.1 1.94 2.74
Subscription required - Subscription is required.

Reserves at December 31, 2019:

CategoryTonnage CommodityGradeContained Metal
Proven 1,167 kt Gold 0.62 g/t 23 koz
Probable 53,468 kt Gold 0.57 g/t 981 koz
Proven & Probable 54,635 kt Gold 0.57 g/t 1,004 koz
Measured 6,567 kt Gold 0.46 g/t 96 koz
Indicated 175,968 kt Gold 0.49 g/t 2,793 koz
Measured & Indicated 182,535 kt Gold 0.49 g/t 2,902 koz
Inferred 15,000 kt Gold 0.38 g/t 184 koz

Commodity Production Costs:

CommodityUnits2019201820172016201520142013
Cash costs (sold) Gold USD  ......  Subscription required  ......  Subscription required 727 / oz 628 / oz 734 / oz 900 / oz
Total cash costs (sold) Gold USD 638 / oz 743 / oz 909 / oz 907 / oz
All-in sustaining costs (sold) Gold USD  ......  Subscription required  ......  Subscription required 727 / oz 979 / oz 1,156 / oz 1,266 / oz 1,108 / oz
Subscription required - Subscription is required.

Financials:

Units201920172016201520142013
Sustaining costs M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required 53.2   33.2   17.4  
Revenue M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required 152.9   102.4   113.7  
Operating Income M USD  ......  Subscription required  ......  Subscription required 11.5   -19.8   -9.3  
Subscription required - Subscription is required


Heavy Mobile Equipment as of December 31, 2018:
HME TypeModelSizeQuantity
Loader ....................... Subscription required 28 cu. yd 1
Loader (FEL) ....................... Subscription required 26 cu. yd 2
Shovel (hydraulic) ....................... Subscription required 44 cu. yd 2
Truck (haul) ....................... Subscription required 205 tons 16
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Sep 21, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 21, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 21, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 21, 2020
Subscription required - Subscription is required.

Staff:

EmployeesContractorsYear
Subscription required 2017
Subscription required Subscription required 2016

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2018
................................... Subscription required 2018
................................... Subscription required 2018
................................... Subscription required 2018
................................... Subscription required 2018
Annual Information Form 2017
Financial Review 2017
Year-end Mineral Reserves 2017
Annual Information Form 2016
Corporate Presentation 2016
Corporate Presentation 2016
Fact Sheet 2016
Financial Review 2016
Annual Report 2015
Financial Review 2014
Technical Report 2014
Subscription required - Subscription is required.

News:

NewsDate
Equinox Gold Increases Mesquite Reserves by 28% and Measured & Indicated Resources by 94% October 8, 2020
Equinox Gold Closes US$75 Million Equity Financing for Acquisition of Mesquite Gold Mine October 12, 2018
Equinox Gold to Acquire the Mesquite Gold Mine in California for $158 Million September 20, 2018

Aerial view:

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