The Moss mine extracts gold and silver from ore via heap leaching. Mined ore is crushed to a P80 of approximately 3/8" inch (80 mm) and conveyed to a pad. Following stacking, the ore is irrigated with a dilute sodium cyanide solution via drip emitter. The solution passes through the heap leach pad and exits the bottom. As it travels through the heap, the solution dissolves gold and silver. The solution discharging from the heap is loaded with dissolved gold and silver and is referred to pregnant solution. The pregnant solution flows from the heaps or is pumped to a pregnant solution pond. From the pregnant solution pond, it is pumped to the Merrill-Crowe plant. The pregnant solution passes through clarifier filters to remove any entrained solids from the solution. The oxygen content in the solution is then decreased by passing through a deaeration tower. Zinc dust is added to the discharge solution from the deaeration tower. The dissolved gold and silver plates onto the zinc dust and forms a precipitate. The solution passes through plate and frame filter presses where the precious metal bearing precipitate is removed. The discharge solution from the precipitate filters is referred to as barren solution, which reports to the barren solution tank. Sodium cyanide is added to the barren solution to the target concentration, and then the barren solution is pumped back to the heap leach pad for further leaching.
The precipitate from the filters is removed and collected in pans. The pans are placed in ovens where the precipitate is dried. The dried precipitate is mixed with fluxes and smelted in a furnace to produce doré bars for sale to refiners.
Key Facts
Location: Mohave Country, Northwestern Arizona Mine Type: Open Pit Metals Mined: Au and Ag Employees/Contractor: 125 Deposit Type: Fault-hosted epithermal quartz-calcite veins with associated vein stockwork Ownership: 100% Reserves and Resources: See Technical Report
Summary
The Moss Gold Mine is an open-pit, heap-leach operation located in the historic Oatman District of northwestern Arizona, approximately 1.5 hours south of Las Vegas, Nevada. The mine has produced gold since 2018 and holds significant potential for both near-mine and regional resource expansion. Following its integration into Mako Mining’s portfolio in March 2025, the Company plans to restart mining operations, optimize the mine plan, and de-bottleneck processing facilities to improve efficiency and gold recoveries. With strong infrastructure and all operating permits in good standing, Moss represents a key growth platform in Mako’s strategy to build a profitable, multi-asset gold producer in the Americas.
Operating Metrics
2023
2022
2021
2020
2019
Tons Processed (tonnes)
2,798,293
2,976,281
2,757,861
2,475,980
2,046,026
TPD (tonnes per day)
7,773
8,267
7,661
6,878
5,683
Operating Data
2023
2022
2021
2020
2019
Total Mineral Mined (tonnes)
8,057,304
8,449,785
8,434,837
7,655,031
6,142,598
Waste (tonnes)
5,310,084
5,486,747
5,624,800
5,217,216
4,218,222
Ore Mined (tonnes)
2,747,220
2,963,038
2,810,037
2,437,815
1,924,376
Strip Ratio (waste/ore)
1.93
1.85
2.00
2.14
2.19
Gold Produced (Ounces)
31,047
31,094
29,107
42,116
28,558
Silver Produced (Ounces)
202,060
160,480
229,212
361,805
182,788
Au Grade (grams/tonne)
0.47
0.45
0.43
0.66
0.71
Ag Grade (grams/tonne)
6.8
3.47
5.95
11.29
11.91
Geology and Mineralization
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. 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 focused on the main Moss vein and associated vein stockwork.
Photo Gallery
USA - Moss Mine
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Mako Mining Corp.
838 West Hastings St.
Suite 700
Vancouver, BC V6C 0A6 info@makominingcorp.com