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Mexico
Bolivar (Expansion) Project (Bolivar Mine)

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 Location:
54 km NE from Choix, Chihuahua, Mexico

  Project Contacts:
Blas Cano de los Rios #500 Col. San Felipe
Chihuahua
Chihuahua, Mexico
31203
Phone  ...  Subscription required
WebsiteWeb
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  • Overview
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  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Fleet
  • Personnel
  • Filings & News

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Overview

StagePreliminary Economic Assessment
Mine TypeUnderground
Commodities
  • Gold
  • Silver
  • Copper
Mining Method
  • Sub-level stoping
Processing
  • Flotation
Mine Life14 years (as of Jan 1, 2019)
Sierra Metals has selected the 10,000 tpd (2024) production rate as the preferred option for Bolivar Expansion.
Latest NewsSierra Metals Announces Filing of NI 43-101 Technical Report on the Preliminary Economic Assessment to Double Output at Its Bolivar Mine...     November 5, 2020


Owners & OPERATOR

Source: p. 14
CompanyInterestOwnership
Sierra Metals Inc. 100 % Indirect
Dia Bras Mexicana SA de CV (operator) 100 % Direct
The Bolivar property is owned by Sierra Metals, formerly known as Dia Bras Exploration, Inc., through subsidiary companies Dia Bras Mexicana S.A. de C.V. and EXMIN S.A. de C.V. (collectively Dia Bras).

Deposit Type

  • Skarn
  • Breccia pipe / Stockwork
  • Vein / narrow vein
  • Carbonate hosted


Summary:

The Bolivar deposit is classified as a high-grade Cu-Zn skarn and exhibits many characteristics common to this type of deposit. The term ‘skarn’ refers to coarse-grained calcium or magnesian silicate alteration formed at relatively high temperatures by the replacement of the original rock, which is often carbonate-rich.

Mineralization at the Bolivar Property is hosted by skarn alteration in carbonate rocks adjacent to the Piedras Verde granodiorite. Orientations of the skarn vary dramatically, although the majority are gently-dipping. Thicknesses vary from 2 m to over 20 m. Skarn mineralization is strongly zoned, with proximal Cu-rich garnet skarn in the South Bolivar area, close to igneous contacts, and more distal Zn-rich garnet+pyroxene skarn in the northern Bolivar and southern skarn zones near El Val. The presence of chalcopyrite+bornite dominant skarn (lacking sphalerite) in the South Bolivar area, along with K-silicate veins in the adjacent granodiorite suggests that this zone is close to a center of hydrothermal fluid activity. In contrast, the main Bolivar Mine is characterized by Zn>Cu and more distal skarn mineralogy such as pyroxene>garnet and pale green and brown garnets. Alteration is zoned relative to fluid flow channels. From proximal to distal, the observed sequence is red-brown garnet to brown garnet with chalcopyrite ± bornite ± magnetite to green garnet ± pyroxene with chalcopyrite + sphalerite to massive sulfide (sphalerite ± chalcopyrite ± galena) to marble with stylolites and other fluid escape structures.

Mineralization exhibits strong stratigraphic control and two stratigraphic horizons host the majority: an upper calcic horizon, which predominantly hosts Zn-rich mineralization, and a lower dolomitic horizon, which predominantly hosts Cu-rich mineralization. In both cases, the highest grades are developed where fault or vein structures and associated breccia zones cross these favorable horizons near skarn-marble contacts. Zones of breccia follow faults like the Rosario, Fernandez, and Breccia Linda trends as well as nearly vertical breccia pipes such as La Increible.rly vertical breccia pipes.


Mining Methods

  • Sub-level stoping


Summary:

Using the resources estimated by SRK Consulting through December 2019, Sierra Metals performed a growth analysis to determine how the Bolívar Mine could achieve sustainable production of 7,000 tpd - 15,000 tpd. The analysis indicates that the production objectives are achievable through the expansion of the sub-level stoping mining method in the new production areas, which will allow the sustainability of the operation. A new configuration of the mining method will allow greater recovery of resources and production rates.


Crushing and Grinding
Crusher / Mill TypeModelSizePowerQuantity
Jaw crusher ....................... Subscription required 93 kW 1
Cone crusher ....................... Subscription required 336 kW 1
Cone crusher ....................... Subscription required 224 kW 1
Ball mill ....................... Subscription required 9.5' x 14' 447 kW 2

Summary:

The Piedras Verdes processing plant can be adapted to process 10,000 tpd and would require:
• Temporary shutdown to overhaul equipment;
• Purchase of mobile jaw and cone crushers; and
• Overhaul and reintroduction of idle equipment.

The crushing stage is supplied with mineralized material hauled from the mine site using contractor operated haul trucks. A typical haul truck has approximately 20 tonnes capacity and delivers mineralized material from the mine area to the primary crusher’s mineralized material stockpiling area. Trucks can dump directly to the primary crusher or alternatively, to one of several stockpiles. Typically, a front-end loader reclaims mineralized material from the stockpiles and then feeds the jaw crusher.

The crushing plant is fed through a hopper equipped with a 20-inch x 20-inch static grizzly that discharges to a jaw crusher operating in open circuit. The nominal four-inch material discharging from the jaw crusher is classified by two double-deck vibrating screens. The top screen is two inches by one inch and the bottom screen is 3/4 inch by 3/8 inch. Material smaller than 3/8 inch becomes the final crushed product that is transferred to two silos having an individual capacity of 1,000 tonnes each. The vibrating screen’s oversize feeds a secondary crushing stage consisting of two cone crushers. The top screen is conveyed to a Sandvik HC660 cone crusher and the bottom screen oversize is conveyed to a Metso HP-300 cone crusher. The cone crusher’s discharge joins the primary crusher’s discharge and feeds the double-deck vibrating screens.

Feed to the grinding circuit is sourced from two 1,000 tonne silos that hold the final crushed product from the crushing plant. The grinding circuit consists of conventional ball mills operating in closedcircuit operation with hydrocyclones. Two 9.5 ft x 14 ft ball mills operate in parallel, each one in closed circuit with a hydrocyclone cluster. The two ball mills underwent complete overhauls during the end of 2017 to improve mechanical availability. The hydrocyclones were changed from D26 to D20 to improve plant stability. The product size in the cyclone overflow ranges between 34% and 48% passing 75 micrometers, with an average size of 43.5% passing 75 micrometers. The hydrocyclone overflow feeds the flotation circuit. The hydrocyclone underflow stream is returned to the ball mills for further size reduction.


Processing

  • Flotation

Flow Sheet: Subscription required

Summary:

Sierra Metals operates the Piedras Verdes conventional concentration plant consisting of crushing, grinding, flotation, thickening and concentrate filtration processes. Thickened flotation tails are placed into a conventional tailings storage facility and the mine is converting to the use of dry-stack tailings in mid-2020. The mill has been upgraded since and the current nominal throughput capacity is 3,500 tpd although the mine has exceeded this throughput on many occasions and in 2020 has achieved 5,000 tpd.

Sierra Metals has selected the 10,000 tpd (2024) production rate as the preferred option for Bolivar Expansion.

The Piedras Verdes processing plant can be adapted to process 10,000 tpd and would require:
• Temporary shutdown to overhaul equipment;
• Purchase of mobile jaw and cone crushers; and
• Overhaul and reintroduction of idle equipment.

The flotation circuit operates three identical parallel flotation lines. Each flotation lin ........


Combined production numbers are reported under Bolivar Mine

Operational Metrics:

Metrics
Daily ore mining rate  ......  Subscription required
Waste tonnes, LOM  ......  Subscription required
Ore tonnes mined, LOM  ......  Subscription required
Total tonnes mined, LOM  ......  Subscription required
Daily processing capacity  ......  Subscription required
* According to 2019 study.
Subscription required - Subscription is required.

Reserves at December 31, 2019:

CategoryTonnage CommodityGradeContained Metal
Indicated 19.4 Mt Gold 0.21 g/t 127.8 koz
Indicated 19.4 Mt Silver 15.1 g/t 9.4 M oz
Indicated 19.4 Mt Copper 0.77 % 149,116 t
Inferred 21.4 Mt Gold 0.21 g/t 145.6 koz
Inferred 21.4 Mt Silver 14.2 g/t 9.8 M oz
Inferred 21.4 Mt Copper 0.78 % 167,077 t

Commodity Production Costs:

CommodityUnitsAverage
Cash costs Copper Equivalent USD  ......  Subscription required *
Assumed price Copper USD  ......  Subscription required *
Assumed price Silver USD  ......  Subscription required *
Assumed price Gold USD  ......  Subscription required *
* According to 2019 study / presentation.
Subscription required - Subscription is required.

Operating Costs:

Units2019
UG mining costs ($/t milled) USD 10.4 *
Processing costs ($/t milled) USD  ......  Subscription required
Total operating costs ($/t milled) USD  ......  Subscription required
* According to 2019 study.
Subscription required - Subscription is required.

2019 Study Costs and Valuation Metrics :

MetricsUnitsLOM Total
Closure costs $M USD  ......  Subscription required
Total CapEx $M USD  ......  Subscription required
UG OpEx $M USD  ......  Subscription required
Processing OpEx $M USD 225.6
G&A costs $M USD 55.4
Total OpEx $M USD  ......  Subscription required
Income Taxes $M USD  ......  Subscription required
Gross revenue (LOM) $M USD  ......  Subscription required
Net revenue (LOM) $M USD  ......  Subscription required
EBITDA (LOM) $M USD  ......  Subscription required
Pre-tax Cash Flow (LOM) $M USD  ......  Subscription required
After-tax Cash Flow (LOM) $M USD  ......  Subscription required
After-tax NPV @ 5% $M USD  ......  Subscription required
After-tax NPV @ 10% $M USD  ......  Subscription required
After-tax NPV @ 8% $M USD  ......  Subscription required
Subscription required - Subscription is required.

Proposed Heavy Mobile Equipment as of December 31, 2019:
HME TypeSizeQuantity
Bolter 5
....................... Subscription required 5
....................... Subscription required ....................... Subscription required 8
....................... Subscription required 17
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Dec 31, 2019
....................... Subscription required ....................... Subscription required Subscription required Nov 16, 2020
Subscription required - Subscription is required.

Staff:

Total WorkforceYear
Subscription required 2019

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2019
................................... Subscription required 2018
Subscription required - Subscription is required.

News:

NewsDate
Sierra Metals Announces Filing of NI 43-101 Technical Report on the Preliminary Economic Assessment to Double Output at Its Bolivar Mine... November 5, 2020

Aerial view:

Subscription required - Subscription is required.

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