Moss Mine

Description

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.