Overview
Stage | Permitting |
Mine Type | Underground |
Commodities |
|
Mining Method |
- Drift & Fill
- Cemented backfill
|
Processing |
- Calcining
- Pressure oxidation
- Carbon in leach (CIL)
- Cyanide (reagent)
- Roasting
|
Mine Life | 8 years (as of Jan 1, 2021) |
The gold deposit defined at McCoy-Cove represents one of the highest-grade deposits with resources in excess of 1 million ounces of gold in North America. McCoy-Cove is permitted for underground development and i-80 will initiate construction of a decline in early 2022 to advance a major underground drill campaign, followed by completion of a full feasibility study.
A previously completed preliminary economic assessment demonstrated the strong economic opportunity at McCoy-Cove and the property is host to substantial infrastructure with road access. |
Latest News | Premier Files Technical Reports for South Arturo and McCoy-Cove Properties February 2, 2021 |
Source:
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i-80 holds 100% interest in the McCoy-Cove project.
Equinox Gold Corp. has completed its acquisition of Premier Gold Mines Limited.
In connection with the acquisition, the spin-out of i-80 Gold Corp. (“i-80 Gold”), a newly created company holding Premier’s gold projects in Nevada, USA, was also completed. Equinox Gold is a 30% shareholder of i-80 Gold.
Deposit Type
- Skarn
- Vein / narrow vein
- Carlin-type
- Carbonate replacement
Summary:
Geology and Mineral Resource The Cove Project contains four structurally controlled mineralized zones within the Triassic sedimentary package. The Helen and Gap zones are Carlin Style disseminated refractory gold deposits. The Cove South Deep (CSD) gold and silver mineralization is associated with disseminated sulfides and is characterized by Ag:Au ratios of 50:1 to over 100:1. The 2201 zone is comprised of disseminated sulfides within sheeted stockwork veins with high concentrations of lead and zinc.
The Cove-Helen deposit consist of two mineralization styles, Carlin-style and polymetallic sheeted veins. The Carlin-style mineralization within the Helen, Gap, and CSD zones comprises approximately 85% of the existing resource with high gold and silver grades occurring as both stratabound and structurally controlled mineralization at the intersection of the Cove anticline and favorable lithologic beds, structures, intrusive dikes and sills.
The polymetallic 2201 zone is a separate deposit from the shallower Carlin-style mineralization and is believed to be a structurally controlled sheeted vein system. Veining is oriented northwest, with vein geometry being controlled by a deeper northwest striking reverse fault. Due to its depth, the 2201 zone has seen limited drilling since its original discovery in late 2013, however, additional infill and step-out drilling in the future will help to better define deposit potential and mineralization controls.
There are four distinct mineralization types known on the property: Carlin-style, polymetallic heeted veins, carbonate replacement (Manto) and skarn. The Helen, Gap and CSD deposits are Carlin-style deposits while the 2201 zone is comprised of steeply dipping polymetallic sheeted veins.
CARLIN-STYLE (AU-AG)
The gold in Carlin-style deposits is usually sub-micron in size and generally occurs in pyrite and arsenical pyrite. An envelope characterized by decalcification, silicification, and argillization accompanied by anomalous amounts of silver, arsenic, antimony, thallium, and mercury often accompanies mineralization. The Carlin-style mineralization at Cove is relatively rich in silver compared to similar deposits elsewhere in northern Nevada (Johnston, 2003). When Carlin-style mineralization occurs in the silty limestones and packstones of the Favret Formation and Home Station Dolomite, decarbonatization replaces fine-grained calcite and/or dolomite with quartz and forms very fine-grained illite and pyrite. Diagenetic pyrite was probably present in the Helen Zone before Carlin-style mineralization based on the abundant presence of subhedral pyrite grains that bear no arsenian rims. The arsenic-bearing pyrite precipitated as a product of Carlin-style mineralization in the Helen are fine-grained (~10 microns) patchy, anhedral “fuzzy” pyrite generally smaller than the diagenetic pyrite grains. In the CSD zone, most pyrite grains in high-grade samples are larger (~20 microns), display spectacular, sharp geochemical zonations, and are rimmed with arsenian pyrite or stoichiometric arsenopyrite. The few samples studied from the Gap under the SEM suggest it shares more in common with the CSD zone though its silver content is lower overall.
POLYMETALLIC SHEETED VEINS (AU-AG±PB-ZN)
The polymetallic veins in the 2201 zone are enveloped by a zone of illitic of the conglomerate matrix detected by sodium cobaltinitrate staining and confirmed by scanning electron microscope (SEM) analysis. Minor silicification is relatively common, especially in the conglomerate, however, it is not present everywhere and not always directly associated with mineralization.
CARBONATE REPLACEMENT (AG-PB-ZN±AU)
Carbonate replacement mineralization occurs as local pods of manto-style mineralization characterized by massive sulfide (pyrite- sphalerite-galena) replacing basal limestone at the Dixie Valley/Favret contact. Mineralization is discontinuous and generally defined by high- grade Ag-Zn-Pb±Au.
SKARN (AU-AG±-CU)
Skarn mineralization at the historic McCoy pit occurs as both endoskarn and exoskarn mineralization characterized by a predominantly garnet-diopside-magnetite mineral assemblage.
The Carlin-style mineralization across the deposit appears to represent an evolving system from a “primary” endmember represented by the CSD zone with higher Ag/Au, coarser-grained pyrite, and a close proximal relationship to Ag-Pb-Zn-(Au) mineralization to the “evolved” endmember represented by the Helen Zone with lower Ag/Au, very fine-grained pyrite, and weak spatial association with any other styles of mineralization. The Gap can be considered a “transition” zone between the two endmembers until more petrography is conducted on the recently discovered Gap to test this hypothesis. Helen Zone geochemistry is distinct from the CSD zone in many ways. For samples greater than 1 ppm Au, less than or equal to 100 ppm Ag, and confirmed to be Carlin-style mineralization by core photo review, the Helen Zone has an average Ag/Au ratio of approximately 0.85 whereas the CSD zone is 2.25. Gold in both the Helen and CSD zones correlates with As, Sb, and Hg, however, Au correlates moderately (0.52 correlation coefficient) with Ag in the CSD zone but more weakly (0.3652 correlation coefficient) in the Helen Zone.
Like the geochemistry, the mineralization in the Helen and CSD is also distinct. The As- bearing (assumed to also be Au-bearing) pyrite in the Helen are generally finer-grained, less euhedral, and more poorly zoned than the As- bearing CSD zone pyrite. Helen pyrite overall have lower As content – ranging from just at detection limit (~0.3 wt% to 0.5 wt%) to 2.1 wt% – than the CSD zone which contains pyrite with arsenic contents ranging from detection limit to 6 wt%. The SEMEDS system first detected trace elements such as Te, Tl, Hg, Sb, and even Au and Ag in CSD zone pyrite, while electron microprobe analysis confirmed the presence of Au, Ag, As, Tl, Hg, Sb, and Pb in CSD mineralization. Other pyrite in the CSD zone contain fewer trace elements but still display complex elemental zoning and growth patterns visible only in backscatter electron imaging. The complicated nature of the mineralized pyrite at the CSD zone is suggestive of a more complex and long-lasting mineralizing event in comparison to the seemingly simple Helen mineralization.
In the 2201 zone, Au correlates with Ag, As, Cu, Fe, Pb, Sb, and Zn – a distinctly different grouping of elements from the CSD, Gap, and Helen Zones. The 2201 zone veins typically occur as sheeted veins and range in thickness from 0.1 cm to 6.5 cm and contain both quartz and carbonate minerals as gangue. Generally, the calcite and dolomite- dominant veins are shallower and thinner whereas the quartz(- carbonate)-bearing veins are deeper and can reach widths of 15 cm. The sulfides are mostly pyrite, sphalerite, and galena with arsenopyrite, chalcopyrite, and pyrrhotite also locally present. Visible gold is mostly limited to the thicker veins and is always observed along the margins with coarse-grained quartz. When microscopic, the gold is present as electrum with approximately 15 wt% Ag (measured on SEM-EDS) and hosted within sulfides such as chalcopyrite or arsenopyrite. Galena may also carry up to 10 wt% Ag. An oriented hole drilled in 2014 (PG14-23) provided some structural data for the vein-type mineralization. There were no trends for veins grouped by gangue or thickness, however, when grouped by depth, the data show that veins shallower than 1,750 feet generally strike northeast-southwest with varying dips and veins deeper than 1,900 feet generally strike northwest-southeast and dip steeply in both directions.
Mining Methods
- Drift & Fill
- Cemented backfill
Summary:
Due to the mostly flat geometry of the ore lenses, all planned production mining will be completed using drift and fill mining. The final choice of mining method will depend upon the geometry of the stope block, proximity to main access ramps, ventilation and escape routes, the relative strength or weakness of the mineralized material and adjacent wall rock, and finally the value or grade of the mineralized material. The choice of mining method will not be finalized until after the stope delineation and definition drilling is completed.
ACCESS DEVELOPMENT
Underground access to the mining areas will begin with a portal on the North side of the existing pit and ramp down. Initial work will consist of 4,557 feet of decline from the portal down to approximately the 4600-foot elevation and 889 feet of drill laterals. The drill laterals are located directly above the Helen and Gap deposits.
Primary access drifts are designed 15 feet wide and 17.5 feet high to permit 30-ton haulage trucks and provide a large cross section for ventilation. Drift gradients will vary from – 15% to + 15% to reach the desired elevation. Secondary drifts, spiral ramps and vertical raises will connect the haulage drifts to provide a pathway for ventilation to the surface and serve as a secondary escape way.
GROUND SUOOPRT
It is expected that Swellex rock bolts along with welded wire mesh will be able to control all conditions encountered during decline development and stoping. Shotcrete will also be liberally applied as needed to prevent long-term deterioration of the rock mass. Under more extreme conditions, resin anchor bolts, or cable bolts can be used to supplement the primary support. Steel sets and spiling may also be used to support areas with the most severe ground conditions.
VENTILATION AND SECONDARY EGRESS
A combination of the main access drifts and vertical raises to the surface are arranged in a manner to provide a complete ventilation circuit capable of supplying the mine with 500,000 cubic feet per minute (CFM) of fresh air. Air movement is facilitated by primary ventilation fans placed at the surface and underground in strategic locations. Small auxiliary fans and ducting will draw primary ventilation air directly into the working faces. Secondary egress will be provided by installing a personnel hoist with a capsule capable of holding up to four people. The hoist will be located at the surface of the exhasut ventilation raise.
DEWATERING
The dewatering wells will provide the majority of mine dewatering. Small localized inflows will be captured at sumps located strategically throughout the mine and pumped to the surface where it will be commingled with the water from the dewatering wells.
DRIFT AND FILL
A drift and fill stope is initiated by driving a waste crosscut from the access ramp to the ore. The initial ore drift is driven at planned 13-feet wide by 13-feet high dimensions, with gradient varying between +/-20% to follow the geometry of the mineralization. The minimum cut and fill drift height is eight feet to minimize dilution on the thinner mineralized lenses. Once the initial drift is driven, floor may be pulled and/or back may be breasted down to capture the full thickness of the lens. Where mining is planned adjacent to the drift, it will be backfilled with CRF (Cemented Rock Fill) prior to mining the subsequent drifts.
Approximately 5,270 feet of development will be undertaken in 2022 and 2023 to provide access for underground delineation and exploration drilling.
Processing
- Calcining
- Pressure oxidation
- Carbon in leach (CIL)
- Cyanide (reagent)
- Roasting
Source:
Summary:
The primary processing option for Helen and Gap resources is toll milling and treating by a third party through either existing roasting operation or an existing pressure oxidation operation (POX). Premier Gold solicited two items from a prospective toll operator with both roasting and POX operations.
The first item included the test protocols and test conditions for laboratory bench scale batch roasting and pressure oxidation tests conditions for the 2017 metallurgical testing. The conditions provided approximate the expected operating conditions in the prospective toll operator’s roasting and POX facilities.
The second item Premier Gold solicited was terms and conditions for toll milling and treating Helen resource material. Premier Gold provided a package of Helen metallurgical data for the roasting and POX tests from the 2017 test program to the prospective toll process operator for their consideration and as the basis for toll processing resource material th ........

Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Gold
|
Head Grade, oz/ton
| 0.3 |
Projected Production:
Commodity | Units | Avg. Annual | LOM |
Gold
|
koz
| 102 | 743 |
All production numbers are expressed as metal in doré.
Operational Metrics:
Metrics | |
Daily mining rate
| ......  |
Daily ore mining rate
| ......  |
Ore tonnes mined, LOM
| ......  |
Total tonnes mined, LOM
| ......  |
* According to 2021 study.
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Reserves at January 1, 2021:
Mineral Resources have been estimated using a gold equivalent cutoff grade of 0.141 opt.
Category | Tonnage | Commodity | Grade | Contained Metal |
Indicated
|
1,110 k tons
|
Gold
|
0.316 oz/ton
|
351 koz
|
Indicated
|
1,110 k tons
|
Silver
|
0.85 oz/ton
|
943 koz
|
Inferred
|
4,262 k tons
|
Gold
|
0.317 oz/ton
|
1,353 koz
|
Inferred
|
4,262 k tons
|
Silver
|
0.602 oz/ton
|
2,565 koz
|
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