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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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  • 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
  • Carbon re-activation kiln
  • Smelting
  • Filter press plant
  • 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

Source: p. 18
CompanyInterestOwnership
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:

The Mesquite Mine is an operating open pit mine with ore processing by heap leaching using a CIC circuit to recover gold. Current mine production is a nominal 178,000 tons per day of total material, including a nominal 50,000 to 68,000 tons per day of ore that is hauled to the leach pad.

Highwall slope angle criteria vary by area and pit. In general, the steepest walls are on the south side of the property and the shallowest in the northeast. In general, the inter ramp angles vary from 29 to 42 degrees depending on pit area and wall orientation. This is due to foliation present parallel to the walls in certain zones.

Four pit and waste dump areas are considered in the reserves statement:
1. Brownie – one phase
2. Vista East- two phases
3. Vista West – one phase
4. Big Chief Waste dump – two parts

Each pit phase has been designed to accommodate the existing mining fleet. Mining occurs on 30 ft. lifts with catch benches spaced every 60 ft. vertically. The haul roads are 100 ft. in width with a road grade of 10%.


Crushing and Grinding


Processing

  • Carbon re-activation kiln
  • Smelting
  • Filter press plant
  • 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 processing facilities were originally designed to process 8,800 gpm of pregnant gold solution producing up to 140,000 oz of gold annually from a combination of 98 million tons of oxide ore grading 0.016 oz/t and 30 million tons of non-oxide ore. Owing to the decreasing head grades as the mine developed, ore stacking, and solution processing rates have increased to maintain the nominal 140,000 ounce per annum production rate. Nominal solution flows to and from the heap are c. 13,400 gpm of barren solution to the heap and c. 12,000 of pregnant solution to the ADR circuit. The difference between the two flows accounts for fresh ore wetting and evaporation.

The processing facilities include the following operations:
- heap leaching
- carbon adsorption using carbon-in-column (CIC) processing
- desorption and gold recovery
- reagents and utilities
- waterservices

During early operations, the ore was crushed to a nominal 2-inch ........

Recoveries & Grades:

CommodityParameter201920182017201620152014
Gold Head Grade, g/t  ......  Subscription required  ......  Subscription required0.320.380.340.4

Production:

CommodityUnits2019201820172016201520142013
Gold oz  ......  Subscription required155,260168,889111,123134,868106,670107,016
All production numbers are expressed as metal in doré.
Subscription required - Subscription is required.

Operational Metrics:

Metrics20192017201620152014
Ore tonnes mined  ......  Subscription required20,828 kt18,969 kt19,987 kt13,550 kt
Waste  ......  Subscription required38,023 kt39,782 kt38,791 kt37,107 kt
Stripping / waste ratio  ......  Subscription required1.83 2.1 1.94 2.74
Daily mining rate  ......  Subscription required
Daily ore mining rate  ......  Subscription required
Subscription required - Subscription is required.

Reserves at December 31, 2019:

CategoryTonnage CommodityGradeContained Metal
Proven 0.228 Mt Gold 1.21 g/t 9 koz
Probable 27.972 Mt Gold 0.64 g/t 575 koz
Proven & Probable 28.2 Mt Gold 0.62 g/t 584 koz
Measured 0.271 Mt Gold 1.08 g/t 9 koz
Indicated 68.164 Mt Gold 0.51 g/t 1,113 koz
Measured & Indicated 68.434 Mt Gold 0.51 g/t 1,123 koz
Inferred 49.966 Mt Gold 0.34 g/t 544 koz

Commodity Production Costs:

CommodityUnits201920182017201620152014
Cash costs (sold) Gold USD  ......  Subscription required 723 / oz 727 / oz 628 / oz 734 / oz 900 / oz
Total cash costs (sold) Gold USD 638 / oz 743 / oz 909 / oz
All-in sustaining costs (sold) Gold USD  ......  Subscription required 819 / oz 727 / oz 979 / oz 1,156 / oz 1,266 / oz
Subscription required - Subscription is required.

Financials:

Units20192017201620152014
Sustaining costs M USD  ......  Subscription required12.8   35.6   53.2   33.2  
Revenue M USD  ......  Subscription required215.7   141.7   152.9   102.4  
Operating Income M USD 32.8   29.4   11.5   -19.8  
Subscription required - Subscription is required


Heavy Mobile Equipment as of December 31, 2019:
HME TypeModelSizeQuantity
Dozer (crawler)
Dozer (rubber tire)
Drill (blasthole) 8.75 inch
Grader
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
Truck (haul) ....................... Subscription required 200 tons 6
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Mar 24, 2021
....................... Subscription required ....................... Subscription required Subscription required Dec 31, 2019
....................... Subscription required ....................... Subscription required Subscription required Dec 31, 2019
....................... Subscription required ....................... Subscription required Subscription required Mar 24, 2021
....................... Subscription required ....................... Subscription required Subscription required Mar 24, 2021
....................... Subscription required ....................... Subscription required Subscription required Mar 24, 2021
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 2020
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
Management Discussion & Analysis 2018
Press Release 2018
Press Release 2018
Quarterly Report 2018
Technical Report 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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