United States

Gunnison Mine

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Overview

Mine TypeIn-Situ
StageRestarting
Commodities
  • Copper
  • Sulphuric acid
Mining Method
  • Solution mining
Mine Life... Lock
SnapshotThe Gunnison Copper Project is the world’s most environmentally friendly base metal mining project.

The injection of mining fluids to the wellfield for copper production started on December 31, 2019 and the Company began the start-up and commissioning phase of the project in January 2020. On April 9, 2020 a decision was made to place the project on Care and Maintenance in response to the COVID-19 global pandemic.

Excelsior has recently commenced the ramp-up phase leading to commercial production at the Gunnison Project and has achieved first copper production. However, due to issues related to ramp-up copper production has not yet reached levels that are economically viable.

Excelsior anticipates that with the Gunnison Project commencing production and if appropriate, it acquires additional mineral rights, Excelsior will experience significant growth in its operations.

Well stimulation trials are going to be completed in Q2 2024.

Owners

SourceSource
CompanyInterestOwnership
Excelsior Mining Corp. 100 % Indirect
The Gunnison Project is held by Excelsior Mining Corp. through is wholly-owned subsidiaries Excelsior Mining Arizona, Inc. (Excelsior Arizona) and Excelsior Mining JCM, Inc. (Excelsior JCM).

Contractors

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Deposit type

  • Skarn

Summary:

The Gunnison Project (North Star) lies on the eastern edge of the Little Dragoon Mountains.

The North Star copper deposit is a classic copper skarn (Einaudi et al, 1980 and Meinert et al, 2005).

The North Star deposit is covered by un-mineralized basin fill, varying between 300 and 800 feet in thickness. The mineralized Paleozoic host rocks below the basin fill strike approximately north-northwest and dip 20° to 45° eastnortheast. Baker (1953) recognized three sets of faults in the Johnson Camp area and similar faults have been interpreted in the North Star area. These faults include the “Northeaster” (N10° to 30°E striking; 70° to 75° dip to the SE), “Easter” (N60°E to S60°E striking; 30° to 50° S and higher angle reverse faults dipping 75°S) and “Northwestern” orientations (N15° W strike; steep E or W dip). Only minor displacements are thought to have occurred in the North Star area; however numerous sheared and brecciated faults, generally filled with copper-oxide mineralization, cut through the deposit.

The Paleozoic host rocks have been intruded by the Texas Canyon quartz monzonite along the western margin of the deposit. The intrusion has formed wide zones of calc-silicate and hornfels alteration, as well as extensive low-grade copper sulfide mineralization within the Paleozoic rocks. Metamorphic alteration grading outward from the stock includes garnet-wollastonite-idocrase, diopside, tremolite and chlorite-talc (Kantor, 1977) (Figure 7-3). More specifically, the Martin Formation grades from a wollastonite-diopside-rich rock near the porphyry, to a distal diopsidetremolite-actinolite assemblage, and finally to dolomite. The Abrigo has garnet-actinolite-epidote-diopside alteration with some biotite hornfels near the porphyry, and this grades to a distal tremolite alteration leading into unmetamorphosed limey shale. Quartz-orthoclase-carbonate ± magnetite and chalcopyrite veins are characteristic of the lower Abrigo where it is mineralized.

At North Star, the mineralized formations strike approximately N10° to N40° W and dip from 30° to 45° NE. The strong regional trend of N10° to N30° E striking normal faults is overprinted by an abundance of N10° to N40° W striking reverse faults, joint sets, and normal faults which range in dip from 35° NE, sub-parallel to bedding, to 75° NE. The reverse faults strike parallel to the long axis of the deposit. Late-stage N70° E to S70° E striking vertical faults at the north end of the deposit contain local zones of high-grade copper-oxide mineralization. Porphyritic quartz monzonite intrusions occur along the western margin of the mineralization. At the southern end, the intrusion forms a sill between the Lower Abrigo Formation and the Bolsa Quartzite. At the northern end of the deposit, the intrusion commonly occurs as thin dikes and sills which cut the strata in numerous locations.

MINERALIZATION
Within the Project area the important mineralized host rocks include the Abrigo and Martin Formations and, to a lesser extent, the Horquilla Limestone, and the lower parts of the Escabrosa Limestone. Mineralization is also found in the Bolsa Quartzite and Precambrian basement rocks. Copper mineralization is related to calc-silicate skarns that have replaced these carbonate rocks adjacent to the Texas Canyon quartz monzonite (TQM).

Oxidation has occurred to a depth of approximately 1,600 feet and has resulted in the formation of dominantly chrysocolla with minor tenorite, copper oxides, and secondary chalcocite. Copper-oxide mineralization is present in the calc-silicate skarns as fracture coatings and vein fillings mainly in the form of chrysocolla. The remainder of the oxide mineralization occurs as replacement patches and disseminations. Copper-oxide mineralization extends over a strike length of 11,100 feet, has an aerial extent across strike of up to 3,000 feet and is more than 900 feet thick in places.

Copper sulfide mineralization has formed preferentially in the proximal (higher metamorphic grade) skarn facies, particularly within stratigraphic units such as the Abrigo and Martin Formations, and within structurally complex zones. There are three types of sulfide mineralization within the skarns. In decreasing order of abundance these are fracture coatings and vein fillings, distinct quartz-orthoclase-carbonate ± magnetite and chalcopyrite veins 0.2 to 10 cm wide (Weitz, 1976), and disseminations. The veins have retrogressive haloes of chlorite, actinolite and epidote. Primary mineralization also occurs as stringers and veinlets of chalcopyrite and bornite.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

Milling equipment has not been reported.

Processing

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Production

CommodityProductUnitsAvg. AnnualLOM
Copper Cathode M lbs 1252,154
Sulphuric acid t 1,288

Production Costs

CommodityUnitsAverage
Cash costs Copper USD  ....  Subscribe
Total cash costs Copper USD  ....  Subscribe
All-in costs Copper USD  ....  Subscribe
Assumed price Sulphuric acid USD  ....  Subscribe
Assumed price Copper USD  ....  Subscribe
* According to 2023 study / presentation.

Project Costs

MetricsUnitsLOM Total
Initial CapEx $M USD  ......  Subscribe
Sustaining CapEx $M USD  ......  Subscribe
Closure costs $M USD  ......  Subscribe
Total CapEx $M USD  ......  Subscribe
Well Field OpEx $M USD  ......  Subscribe
G&A costs $M USD 199.5
Total OpEx $M USD  ......  Subscribe
Income Taxes $M USD  ......  Subscribe
Royalty payments $M USD  ......  Subscribe
Net revenue (LOM) $M USD  ......  Subscribe
Pre-tax Cash Flow (LOM) $M USD  ......  Subscribe
After-tax Cash Flow (LOM) $M USD  ......  Subscribe
Pre-tax NPV @ 10% $M USD  ......  Subscribe
Pre-tax NPV @ 7.5% $M USD  ......  Subscribe
After-tax NPV @ 10% $M USD  ......  Subscribe
After-tax NPV @ 7.5% $M USD  ......  Subscribe
Pre-tax IRR, %  ......  Subscribe
After-tax IRR, %  ......  Subscribe
Pre-tax payback period, years  ......  Subscribe
After-tax payback period, years  ......  Subscribe

Heavy Mobile Equipment

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Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Nov 21, 2023
....................... Subscription required ....................... Subscription required Subscription required Nov 21, 2023

Total WorkforceYear
...... Subscription required 2023

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