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United States

Sunshine Mine

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Overview

Mine TypeUnderground
StageRestarting
Commodities
  • Silver
  • Copper
  • Lead
  • Zinc
  • Antimony
Mining Method
  • Underhand Cut & Fill
  • Overhand Cut & Fill
  • Longhole stoping
  • Overhand stoping
  • Alimak
Backfill type ... Lock
Mine Life... Lock
SnapshotSunshine Complex is composed of the Sunshine Mine and the Sunshine Refinery, located in Kellogg, Idaho. The Sunshine Mine property hosts one of the highest-grade, large primary silver deposits in the world.

The Sunshine Mine is an existing underground mine with more than 100 years of operating history. Mine operations have largely been suspended following a succession of bankruptcies by prior operators. The last activity at the mine was in 2008.

An updated MRE 2023 has been reported using the newly developed 3D geological model with appropriate estimation methodology and classification of resources to industry standards. SRK Consulting recommends continued advancement of the Project toward delivery of an updated PEA based on the current MRE. In advance of the next phase of resource and exploration drilling, as well as the start of underground development, SRK recommends that care and maintenance of existing infrastructure be continued to support future work phases at Sunshine.

Owners

SourceSource
CompanyInterestOwnership
Sunshine Silver Mining & Refining Corp. 100 % Indirect
The Sunshine Mine Project is owned by Silver Opportunity Partners LLC, a wholly owned subsidiary of Sunshine Silver Mining & Refining Corporation (SSMRC).

Contractors

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Deposit type

  • Vein / narrow vein
  • Mesothermal

Summary:

Regional Geology
The Coeur d’Alene Mining District is hosted in Precambrian (approximately 1.45 billion years old) metasedimentary rocks of the Belt Supergroup. For silver mineralization targeting, rocks of the Burke, Revett, and St. Regis Formations are prospective and belong to the Ravalli Group within the Belt Supergroup. These Middle Proterozoic rocks cover a large area of northern Idaho and western Montana with up to a 12.5-mile (20-km) thick layer of fine-grained siliciclastic strata. The Sunshine Mine and other Silver Valley deposits occur between the Osburn and Placer Creek faults that are significant regional-scale, east-to-west structures. The regional continuity of the Idaho Silver Belt mineralized system occurs along a strike length of over 20 miles.

Local and Property Geology
The Sunshine Mine is predominantly hosted in the St. Regis Formation, which is over 600 ft thick, and upper strata of the underlying Revett Formation. The lithostratigraphic boundary between these units is unclear. Rock types in the St. Regis are mainly argillite and siltite, which grade to siltite and quartzite in the Revett Formation. Both host units are intensely folded and faulted and metamorphosed to lowgrade, greenschist facies.

The Project area is bisected by several east-to-west faults, namely Polaris, Syndicate, C Fault, and, further south, the Alhambra Fault. Kinematics and rock fabric in the mine are reported to show dip-slip movement on the faults, even though the regional structural setting suggests that movement was strike-slip. Polaris is a normal fault, while the remainder have reverse displacement. The faults at Sunshine are variably mineralized. The C Fault is an example of a well-mineralized structure.

Dominant veins in the mine strike generally east-to-west between the faults and dip steeply (>60°) to the south. Subordinate veins are interpreted to crosscut between the major veins. The larger vein structures are quite extensive and can be traced over long strike distances and depths. Generally, mineralized veins vary between 1 to 5 ft thick with thicknesses pinching and swelling along strike. The strike length of individual veins has been tested up to 2.5 miles in length. Veins at Sunshine can continue from surface to over a mile deep.

Significant Mineralized Zones
Over 35 veins have been named and mined at the Sunshine Mine. Historically, mined grades are exceptionally high in some areas, with averages over 100 opt Ag. The Sunshine and Chester Veins are particularly well endowed, with each reported to have produced over 90 million (M) oz of silver to date. Mineralization is comprised of tetrahedrite, galena, and sphalerite, with typical gangue minerals of siderite, quartz, pyrite, and magnetite. Similar to other deposits in the Idaho Silver Valley, two main vein assemblages are distinguished, which tend to dominate certain areas of the mine: silver-copper veins and lead-zinc veins.

Deposit Type
Mineral Deposit
The deposits of the Coeur d’Alene District, including Sunshine, are classified as clastic metasedimenthosted, silver-lead-zinc mesothermal vein deposits. In addition to Coeur d’Alene, a world-class silver district, this deposit type includes several historical mining localities globally, including the Harz Mountains and Freiberg in Germany, Keno Hill and Kokanee Range in Canada, and Príbram in the Czech Republic. These deposits are typified by the following general characteristics:
• Deposits are hosted in thick sequences of fine- to medium-grained clastic sedimentary rocks transected by deep-seated regional-scale faulting.
• Sedimentary basins occur in a wide range of tectonic environments, but all have been subject to deformation, intrusion, and regional metamorphism, typically greenschist facies.
• Economic minerals are predominantly galena and sphalerite with minor accessory pyrite and a wide range of sulphosalt minerals, including tetrahedrite, pyrargyrite, stephanite, bournonite, acanthite, and native silver.
• Gangue minerals are comprised of siderite and quartz, with lesser amounts of dolomite or calcite.
• Temperature of sulfide mineral deposition is in the range of 250 degrees Celsius (°C) to 300°C.

It is generally accepted that the veins of the Coeur d’Alene District were formed during the Cretaceous to early Tertiary. Genesis of the orebodies may have been a result of regional-scale metamorphism and the development of hydrothermal systems associated with the emplacement of the Idaho Batholith pluton and concurrent deformation. Metamorphic hydrothermal fluids most likely scavenged syngenetic metals (silver, lead, zinc, and copper) from Proterozoic Belt Supergroup strata and emplaced these metals within pre-existing or concurrent structural features.

Geological Model
The signature for all economic deposits discovered within the Coeur d’Alene District is vein-like morphology hosted within the metasediments of the Belt Super Group. Within the Sunshine Mine, as well as other sub-districts in the Coeur d’Alene District, veins occur as branching fissures that crosscut the sedimentary host rocks. Previous studies have indicated the veins are of mesothermal origin.

The vein structures are known to branch or split, forming duplexing, and have anastomosing geometries. The majority of veins strike west, are steeply dipping, elongated down-dip, and can have strike lengths over 4,000 ft and dip lengths over 8,000 ft.

SRK incorporated Sunshine-provided geologic interpretations from the company’s internal experts, regarding the trends of vein domains and mineralization continuity. The QP for mineral resources considers the current geological model to be sufficient for conceptual exploration targeting, geological modeling, and resource estimation of the Sunshine deposit.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

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Processing

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Production

CommodityProductUnitsAvg. AnnualLOM
Silver Concentrate kt 138
Silver Metal in concentrate koz 9,115255,224
Copper Metal in concentrate lbs 1,405,60839,357,029
Lead Concentrate kt 218
Lead Metal in concentrate M lbs 2.262
Antimony Metal in concentrate lbs 66,380,493

Operational metrics

Metrics
Daily ore mining rate  ....  Subscribe
Daily processing capacity  ....  Subscribe
Annual processing capacity  ....  Subscribe
Waste tonnes, LOM  ....  Subscribe
Ore tonnes mined, LOM  ....  Subscribe
Tonnes processed, LOM  ....  Subscribe
* According to 2020 study.

Production Costs

CommodityUnitsAverage
Cash costs Silver USD  ....  Subscribe
Total cash costs Silver USD  ....  Subscribe
Assumed price Lead USD  ....  Subscribe
Assumed price Copper USD  ....  Subscribe
Assumed price Silver USD  ....  Subscribe
* According to 2020 study / presentation.
** Net of By-Product.

Operating Costs

CurrencyAverage
UG mining costs ($/t milled) USD  ....  Subscribe
Processing costs ($/t milled) USD  ....  Subscribe
G&A ($/t milled) USD  ....  Subscribe
Total operating costs ($/t milled) USD  ....  Subscribe
* According to 2020 study.

Project Costs

MetricsUnitsLOM Total
Initial CapEx $M USD  ......  Subscribe
Working capital $M USD  ......  Subscribe
Sustaining CapEx $M USD  ......  Subscribe
Closure costs $M USD  ......  Subscribe
UG OpEx $M USD  ......  Subscribe
Processing OpEx $M USD 270.1
Refining costs $M USD  ......  Subscribe
G&A costs $M USD 219.8
Total OpEx $M USD  ......  Subscribe
Income Taxes $M USD  ......  Subscribe
Royalty payments $M USD  ......  Subscribe
Gross revenue (LOM) $M USD  ......  Subscribe
Net Operating Income (LOM) $M USD  ......  Subscribe
After-tax Cash Flow (LOM) $M USD  ......  Subscribe
After-tax NPV @ 5% $M USD  ......  Subscribe
After-tax NPV @ 7.5% $M USD  ......  Subscribe
After-tax NPV @ 2.5% $M USD  ......  Subscribe
After-tax IRR, %  ......  Subscribe
After-tax payback period, years  ......  Subscribe

Heavy Mobile Equipment

Fleet data has not been reported.

Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Nov 20, 2024
....................... Subscription required ....................... Subscription required Subscription required Nov 20, 2024
....................... Subscription required ....................... Subscription required Subscription required Jan 17, 2020
....................... Subscription required ....................... Subscription required Subscription required Jan 17, 2020
....................... Subscription required ....................... Subscription required Subscription required Nov 20, 2024

Total WorkforceYear
...... Subscription required 2020

Aerial view:

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