The Moss Mine is currently mining the Moss vein system, which consists of fault-hosted epithermal quartz-calcite veins with associated vein stockwork that are younger than and cut across the Moss quartz monzonite porphyry host rock in the vicinity of the mine (see Moss Mine Geology Map). The Moss vein system includes the Moss and Ruth veins, as well as associated hanging wall and, locally, footwall vein stockwork. The Moss vein strikes slightly north of west (~275-285 degrees) and dips steeply (~70-75 degrees) to the south in the vicinity of the mine. Locally, the Moss vein develops a more northerly strike. The Ruth vein, which is approximately 175 meters to the south of the Moss vein on surface, is sub-parallel to, and dips moderately (~50-60 degrees) north towards the Moss vein, with the distance between the two veins diminishing with depth. The two veins intersect at depths of between 180 meters and 230 meters below the current surface. Moss vein hanging wall stockworks are present both above and below the intersection between the two veins. Mining is currently focussed on the main Moss vein and associated vein stockwork.
The Moss mine extracts gold and silver from ore via heap leaching. Mined ore is crushed to P80 of 1/4 inch, mixed with pebble quick lime and conveyed to heaps where it is stacked. Following stacking, the leach pads are irrigated with dilute sodium cyanide solution. Gold and silver are dissolved as the sodium cyanide solution passes through the leach pads. The solution (referred to as pregnant solution) exits the leach pads and flows to a pregnant solution pond. From the pregnant solution pond, the solution is passed through a Merrill-Crowe plant where the gold and silver are precipitated out of solution using zinc powder. The precipitate is filtered, dried, and smelted to produce doré bars.
The maiden Proven and Probable Mineral Reserve for the Moss Mine, estimated effective July 1, 2021, is presented in the following table. The Proven and Probable Reserve estimate was constrained by the existing infrastructure of the mine. In the future, infrastructure may be relocated to allow the Moss Mine to realize the full economic benefits of the additional near mine mineralization being defined by the ongoing exploration drilling program.
Proven and Probable Mineral Reserve Effective, July 1, 2021
Classification | Ore (ktonnes) | Gold (g/t) | Silver (g/t) | Contained Gold (000’s oz) | Contained Silver (000’s oz) |
---|---|---|---|---|---|
Proven | 4,611 | 0.46 | 5.8 | 68.1 | 858.8 |
Probable | 8,133 | 0.44 | 5.1 | 116.4 | 1,342.0 |
Proven + Probable | 12,744 | 0.45 | 5.4 | 184.5 | 2,200.8 |
Notes: Metal Prices used for Mineral Reserves: $1,525/oz gold; $18.50/oz silver. Reserves are tabulated at a 0.21 g/t gold cutoff grade. The topography date used for tabulating the Mineral Reserve is 1 July 2021 Metric tonnages and grades are reported: Ktonnes are 1,000 metric tonnes; g/t is grams per metric tonne. The Mineral Reserve estimate was prepared by Jacob Richey, of Independent Mining Consultants Inc. Numbers may not tally exactly due to rounding. The Mineral Reserve estimate was prepared in accordance with CIM Definition Standards.
The Mineral Resource estimate for the Moss mine also has an effective date of July 1, 2021 and is presented in the following table. The Mineral Resource was estimated using drilling available up to May 24, 2021. The component of the mineralization that has reasonable prospects of economic extraction was estimated using the Lerchs-Grossman algorithm. The July 1, 2021 Mineral Resource represents a 36% increase in Measured and Indicated Resources when compared to the December 2019 Mineral Resource Estimate (see 2021 Technical Report). Additional exploration drilling is targeting further expansion of the Mineral Resources along strike and at depth.
Moss Mine Mineral Resource Estimate as at July 1, 2021
Classification | Cut-off Grade (g/t Au) | Tonnage (ktonnes) | Gold (g/t) | Silver (g/t) | Contained Gold (000’s oz) | Contained Silver (000’s oz) |
---|---|---|---|---|---|---|
Measured | 0.15 | 8,398 | 0.40 | 5.1 | 107.4 | 1,389.0 |
Indicated | 0.15 | 30,460 | 0.39 | 4.5 | 382.8 | 4,365.0 |
Measured + Indicated | 0.15 | 38,857 | 0.39 | 4.6 | 490.2 | 5,754.0 |
Inferred | 0.15 | 6,562 | 0.35 | 4.5 | 73.8 | 940.0 |
Notes: The Mineral Resource is inclusive of the Mineral Reserve. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability. The Mineral Resource was prepared in accordance with CIM Definition Standards. Metal prices used for the Mineral Resource: $1,800 per ounce gold and $22.00 per ounce silver. Numbers may not tally exactly due to rounding. Metric tonnages and grades are reported: ktonnes are 1,000 metric tonnes; g/t is grams per metric tonne. The Mineral Resource estimate was prepared by Jacob Richey of Independent Mining Consultants Inc.
An update to the NI 43-101 is in progress and expected to be released at the end of 2023.
Epithermal vein systems on the approximately 165 square kilometer Moss property are associated with right-lateral Walker Lane transtensional structures. The vein systems are hosted in and cut magmatic, volcanic, and volcaniclastic rocks associated with the formation of the Miocene Silver Creek Caldera. More than two million ounces of gold and one million ounces of silver were produced from low sulfidation epithermal veins in the historic Oatman District between 1870 and 1980. The Company has identified multiple low sulfidation epithermal veins for follow-up exploration on the broader Moss property using a combination of remote sensing and geophysical techniques in conjunction with the USGS Mineral Resources Data System (see Moss Propterty Regional Exploration Map). Of particular interest is the intersection between the curviplanar eastern margin of the caldera and the right-lateral sigmoidal Walker Lane structures in the Florence Hill and Grapevine areas. Significant advanced argillic alteration and silica ledges, coincident with aeromagnetic geophysical anomalies, is developed at the intersection of these structures. Interestingly, the main historic Oatman District vein system extends from this intersection to the southeast, with the West Oatman and Moss vein systems extending from this intersection to the northwest. The possibility that the low sulfidation epithermal systems and alteration zonation are vectoring back to the potential mineralization source in the structural intersection represents a significant exploration target for the Company. Exploration of the Moss property is following a telescoped approach, from infill drilling at the Moss mine, through near-mine resource definition drilling and along-strike medium- to long-term resource delineation drilling, to true greenfields exploratio