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Peru
Inmaculada Mine

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 Location:
206 km SW from Cusco, Peru

  Regional Office:
Calle La Colonia No. 180 Urb. El Vivero Santiago de Surco
Lima
Peru
Phone  ...  Subscription required
Fax+511-437-5009
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Personnel
  • Filings & News

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Overview

StageProduction
Mine TypeUnderground
Commodities
  • Silver
  • Gold
Mining Method
  • Longitudinal open stoping
  • Cut & Fill
  • Transverse open stoping
  • Cemented backfill
Processing
  • Smelting
  • Calcining
  • INCO sulfur dioxide/air process
  • Vacuum filtration
  • Leaching plant / circuit
  • Agitated tank (VAT) leaching
  • Counter current decantation (CCD)
  • Pressure oxidation
  • Merrill–Crowe
  • Cyanide (reagent)
Mine Life11.3 years (as of Jan 1, 2015)
On November 19, 2021, Peru's government ruled out any operational extensions for Hochschild's flagship Inmaculada silver mine.
Peru's prime minister Mirtha Vasquez said the mines would be closed as soon as possible on environmental concerns, with "no extensions, whether for exploitation, exploration or even shutdown.

However, the Government subsequently affirmed its commitment to upholding the rule of law and acknowledged the continued rights of mining companies to request extensions and modifications of existing permits for mining and exploration activities.
Latest NewsShares of miner Hochschild slump 27%; Peru aide opens door to extensions     November 22, 2021


Owners

Source: p. 17,70
CompanyInterestOwnership
Hochschild Mining Plc. 100 % Indirect
Compañía Minera Ares S.A.C. (operator) 100 % Direct
The Hochschild Mining Plc. holds 100% of Inmaculada gold/silver underground operation.

Deposit Type

  • Epithermal
  • Vein / narrow vein


Summary:

The Inmaculada deposits can be clasified as low to high sulfidation epithermal silver-gold deposits. Deposit sub-types on the Property includes LS type which includes the Au-Ag quartz veins at Quellopata including the Angela Vein, IS type and HS type which includes mineralized breccias at Minascucho, Central and San Salvador and disseminated mineralization at Tararunqui.

Rock chip sampling has shown that consistently high gold vaues (from 1 to over 10 g/t Au) are present in the Angela Vein, in the vicinity of line 10,000N of the local grid.

The Angela Vein outcrops in the central portion of the Quellopata vein system. The vein strikes northeasterly (050º), dips to the southeast (45º to 90º) and outcrops on surface along a strike lenght of 700 m.

The vein varies in thickness from 0.5 m to us much us 16.0 m, and has been tested over a vertical extent of up to 3000 m.

Two generations of mineralization have been observed in the Angela Vein, an early lead-zinc event and a later gold-silver event. The early mineralization consists of white quartz veinlets with sphalerite, galena, pyrite and argentite (minor). These veinlets form a broad, low-grade envelope (0.2 to 1.0% Pb + Zn) which surrounds, and overlaps, the Angela Vein mineralization.

The second mineralizing event at the Angela Vein is the most important economically, and consists of a white chalcedony vein with associated breccia and stockworks. The chalcedony contains small amounts (generally <1%) of electrum, argentite, pyrargyrite, chalcopyrite, pyrite and marcasite.

The Angela Vein is composed of a gangue of white chalcedony, quartz, calcite (minor), smectite and illite. Metallic minerals, which rarely constitute more than 1% of the vein, occur as disseminations and colloform banding, and consist of pyrite, marcasite, argentite, pyrargyrite, chalcopyrite, sphalerite and electrum.


Mining Methods

  • Longitudinal open stoping
  • Cut & Fill
  • Transverse open stoping
  • Cemented backfill


Summary:

- Production has historically come mainly from the Angela vein;
- Exploitation areas are located mainly at three different levels (4300, 4400, 4500m a.s.l);
- The mine has 3 main accesses, which are interconnected;
- Mining methods: Transversal Open Stoping, Longitudinal Open Stoping, Cut and Fill;
- The mine is backfilled with a mix of tailings and cement.


Crushing and Grinding
Flow Sheet: Source
Crusher / Mill TypeModelSizePowerQuantity
Jaw crusher 1.1m x 0.86m 1
SAG mill 6.4m x 3.1m 2000 kW 1
Ball mill 5.5m x 8.53m 4200 kW 1

Summary:

The process flowsheet includes single stage crushing, followed by grinding in a a SAG-ball (SAB) milling circuit, operated in close-circuit with cyclones.

• Ore from the underground mine is crushed using a primary jaw crusher with a close size setting of 115 mm and fed to a stock pile;
• A stock pile with live capacity of 1,920 t to provide crusher product surge capacity prior the SAG mill;
• A 2.0 MW SAG mill with pebble return;
• A 4.2 MW ball mill in closed circuit with hydrocyclones;

Crushing
Run-of-mine (ROM) ore will be dumped from haul trucks or a front-end loader through a 800 mm square-grid static grizzly into the 100 t capacity ROM hopper. Ore is recovered from the ROM bin by a vibrating pan feeder that reports directly to the 1.1 x 0.86 m single toggle jaw crusher. The jaw crusher is designed to operate with a closed side setting of 115 mm and crushes ore to 80% passing (P80) 93 mm. The primary crusher product is conveyed to the crushed ore stockpile.

The crushed ore stockpile will have a live capacity of 1,920 t or approximately 12 hours of mill feed. Three reclaim vibrating feeders will be installed at the base of the crushed ore stockpile to reclaim ore for milling.

Grinding
The grinding circuit selected by Ausenco will be a standard SAB configuration with provision to return SAG mill pebbles to the SAG mill feed. The reclaimed crushed ore will be fed at a controlled rate to a 6.40 m diameter by 3.05 m effective grinding length (EGL) SAG mill. The SAG mill will be equipped with a single 2,000 kW wound rotor induction motor variable speed drive system and single pinion, allowing the mill to operate at 60 - 80% of critical speed.

The ball mill will be equipped with a single 4,200 kW wound rotor induction motor, trommel screen and retractable feed spout/chute. The combined mills discharge slurry will be pumped to the mill cyclone cluster operating in closed circuit configuration with the ball mill. Pregnant solution from the clarifier overflow is added to the cyclone feed hopper to achieve the required cyclone feed pulp density. Mill cyclone underflow will gravitate to the ball mill feed, and cyclone overflow will gravitate to the leach feed vibrating trash screen.


Processing

  • Smelting
  • Calcining
  • INCO sulfur dioxide/air process
  • Vacuum filtration
  • Leaching plant / circuit
  • Agitated tank (VAT) leaching
  • Counter current decantation (CCD)
  • Pressure oxidation
  • Merrill–Crowe
  • Cyanide (reagent)

Flow Sheet: Subscription required

Summary:

The process plant and associated facilities will process run of mine (ROM) ore delivered to the primary crusher, to produce doré bars and tailing. The process encompasses crushing and grinding of the ROM ore, agitated tank cyanidation leaching, a Merril Crowe circuit and smelting of the precipitate to produce doré bars that are then shipped to a refinery for further processing. Following cyanide destruction, the leached taulings will be thickened before placement in the tailings storage facility (TFS) or used as mine backfill.

The flowsheet incorporates the following major process operations:
• 7 x 4,085 m3 live capacity cyanidation leach tanks in series;
• 4 x CCD thickener washing stages and 1 solution clarifier thickener;
• An 810 m3/h Merrill Crowe circuit;
• Retort system to volatilize and remove mercury from the precipitate cake;
• Diesel fired reverbatory smelting furnace;
• Leached tailings cyanide destruction utilizing the INCO SO2 ........

Recoveries & Grades:

CommodityParameter2021202020192018201720162015
Silver Head Grade, g/t  ......  Subscription required  ......  Subscription required  ......  Subscription required150145133115
Gold Head Grade, g/t  ......  Subscription required  ......  Subscription required  ......  Subscription required4.364.154.214.36

Production:

CommodityUnits2022202120202019201820172016
Silver Equivalent koz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required  ......  Subscription required18,58117,72116,948
Gold Equivalent koz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Silver koz  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Gold koz  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
All production numbers are expressed as metal in doré. ^ Guidance / Forecast.
Subscription required - Subscription is required.

Operational Metrics:

Metrics202120202019201820172016
Ore tonnes mined  ......  Subscription required  ......  Subscription required1,338,569 t1,323,525 t1,295,701 t1,306,606 t
Daily processing capacity  ......  Subscription required  ......  Subscription required3,850 t3,850 t3,850 t3,850 t
Subscription required - Subscription is required.

Reserves at December 31, 2021:

CategoryTonnage CommodityGradeContained Metal
Proven & Probable 6,640,030 t Silver 147 g/t 31.4 M oz
Proven & Probable 6,640,030 t Gold 3.5 g/t 741.3 koz
Proven & Probable 6,640,030 t Silver Equivalent 84.7 M oz
Measured & Indicated 7,925,000 t Silver 169 g/t 43.2 M oz
Measured & Indicated 7,925,000 t Gold 4.13 g/t 1,052 koz
Measured & Indicated 7,925,000 t Silver Equivalent 467 g/t 118.9 M oz
Inferred 11,989,000 t Silver 102 g/t 39.2 M oz
Inferred 11,989,000 t Gold 2.57 g/t 988.7 koz
Inferred 11,989,000 t Silver Equivalent 286 g/t 110.3 M oz

Commodity Production Costs:

CommodityUnits2021202020192018201720162015
Total cash costs (sold) Silver USD  ......  Subscription required  ......  Subscription required  ......  Subscription required 5.2 / oz 4.6 / oz
Total cash costs (sold) Gold USD  ......  Subscription required  ......  Subscription required  ......  Subscription required 481 / oz 486 / oz 370 / oz
Total cash costs (sold) Silver USD  ......  Subscription required†  ......  Subscription required†  ......  Subscription required†
Total cash costs (sold) Gold USD  ......  Subscription required†  ......  Subscription required†  ......  Subscription required†
All-in sustaining costs (sold) Silver Equivalent USD  ......  Subscription required  ......  Subscription required  ......  Subscription required 9.9 / oz 9.7 / oz 8.7 / oz 7.3 / oz
All-in sustaining costs (sold) Gold Equivalent USD  ......  Subscription required  ......  Subscription required  ......  Subscription required 731 / oz 721 / oz 646 / oz
^ Guidance / Forecast.
† Net of By-Product.
Subscription required - Subscription is required.

Operating Costs:

Units2021202020192018201720162015
Total operating costs ($/t milled) USD 99.295.193.384.785.464.463.3

Financials:

Units2021202020192018201720162015
Capital expenditures M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required57.7   52.9   54.2   166.3  
Revenue M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required306.1   296.6   280.1   102.3  
Gross profit M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required116.7   74.9   98.7   49.8  
Pre-tax Income M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required116.4   73.7   97.6   49.8  
After-tax Income M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required116.4   73.7   97.6   49.8  
Subscription required - Subscription is required


Heavy Mobile Equipment:

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required May 10, 2022
....................... Subscription required ....................... Subscription required Subscription required May 10, 2022
....................... Subscription required ....................... Subscription required Subscription required May 10, 2022
....................... Subscription required ....................... Subscription required Subscription required May 10, 2022
....................... Subscription required ....................... Subscription required Subscription required May 10, 2022
Subscription required - Subscription is required.


Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
Annual Report 2018
Corporate Presentation 2018
Annual Report 2017
Corporate Presentation 2017
Annual Report 2016
Corporate Presentation 2016
Annual Report 2015
Corporate Presentation 2015
Feasibility Study Report 2012
Subscription required - Subscription is required.

News:

NewsDate
Shares of miner Hochschild slump 27%; Peru aide opens door to extensions November 22, 2021

Subscription required - Subscription is required.

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