Overview
Stage | Permitting |
Mine Type | In-Situ |
Commodities |
|
Mining Method |
|
Mine Life | 24 years (as of Jan 1, 2022) |
The Gunnison Project is a low-cost, environmentally friendly in-situ recovery copper extraction project that is permitted to 125 million pounds per year of copper cathode production. Excelsior announced the start of construction in December 2018, and the completion of the construction phase in December 2019, including the wellfield drilling and the supporting infrastructure. Upgrades to the adjacent Johnson Camp mine (“JCM”) Solvent Extraction and Electrowinning (“SX-EW”) plant were also completed in December 2019. 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. On August 12, 2020 the Company announced that a small-scale restart had commenced. |
Source:
p. 14
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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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). Skarn deposits range in size from a few million to 500 million tonnes and are globally significant, particularly in the American Cordillera. They can be stand- alone copper skarns, which are generally small, or can be associated with porphyry copper deposits and tend to be very large. The North Star deposit is large, at the upper end of the range of size for skarn deposits, and is likely associated with a mineralized porphyry copper system that has not been discovered.
Copper skarns generally form in calcareous shales, dolomites and limestones peripheral or adjacent to the mineralized porphyry. Copper mineralizing hydrothermal fluids are focused along structurally complex and fractured rocks and convert the calcareous shales and limestones to andradite rich garnet assemblages near the intrusive body, and to pyroxene and wollastonite rich assemblages at areas more distal to the stock. Retrograde hydrothermal fluids produce actinolite-tremolite-talc-silica-epidote-chlorite assemblages that overprint earlier garnet and pyroxene. The mineralization is typically pyrite -chalcopyrite-magnetite proximal to the mineralizing porphyry and chalcopyrite-bornite more distally from the body. The copper-gold porphyry and skarn model by Sillitoe (1989) is being used as a conce ........

Summary:
Excelsior proposes to use the In-Situ Recovery (ISR) method to extract copper from oxide mineralization located within the North Star deposit. ISR was chosen based on the fractured nature of the host rock, the presence of water saturated joints and fractures within the ore body, copper mineralization that preferentially occurs along fracture surfaces, the ability to operate in the vicinity of Interstate 10, and to avoid the challenges of open pit mining in an area with alluvium overburden thickness ranging from approximately 300 feet to 800 feet.
In the ISR process, a low pH raffinate solution (“lixiviant”) is injected into the ore body via a series of injection wells. As the lixiviant migrates through the joints and fractures within the mineralized bedrock, copper is dissolved. This pregnant leach solution (PLS) is recovered by a series of recovery wells that surround each respective injection well.
The PLS is pumped to the surface where the copper is stripped from the solution using the solvent extraction/electrowinning (SX-EW) process. The SX-EW process begins with the SX plant extracting and concentrating the dissolved copper from the PLS, after which the EW plant reduces the concentrated copper to copper cathode. Once the copper is recovered by SX, the barren solution is re-acidified with sulfuric acid to create new lixiviant which is pumped back to the well field and re-injected. The total volume of lixiviant injected and PLS extracted will remain ........

Flow Sheet:
Summary:

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Projected Production:
Commodity | Units | Avg. Annual | LOM |
Copper
|
M lbs
| 125 | 2,154 |
All production numbers are expressed as cathode.
Operational Metrics:
Metrics | |
Annual production capacity
| ......  |
* According to 2022 study.
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Reserves at October 1, 2016:
The Mineral Resources are estimated at a 0.05% TCu cut-off for oxide and transitional, 0.30% TCu cut-off for sulfide.
The Mineral Reserve are estimated at a 0.50% TCu cut-off.
Category | Tonnage | Commodity | Grade | Contained Metal |
Probable
|
782.2 M tons
|
Copper
|
0.29 %
|
4,505 M lbs
|
Measured
|
200.7 M tons
|
Copper
|
0.36 %
|
1,439 M lbs
|
Indicated
|
710.8 M tons
|
Copper
|
0.27 %
|
3,875 M lbs
|
Measured & Indicated
|
911.6 M tons
|
Copper
|
0.29 %
|
5,315 M lbs
|
Inferred
|
240.9 M tons
|
Copper
|
0.22 %
|
1,070 M lbs
|
Mine Management:
Job Title | Name | Profile | Ref. Date |
.......................
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.......................
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Jan 9, 2023
|
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Corporate Filings & Presentations:
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