The Moss Mine is an open pit gold-silver mine owned 100% by Elevation Gold Mining via its wholly owned subsidiary Golden Vertex. The mine is located in North-western Arizona, the US.
Elevation Gold (previously Northern Vertex Mining) optioned the mine in 2011 and commenced a pilot testing program in 2014.
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The testing program was followed by a feasibility study in 2015 and a Preliminary Economic Assessment (PEA) in 2017 to extend the life of mine.
Developed in three phases, the construction of the mine commenced in December 2017 and operation in September 2018.
The technical report published in October 2021 extended the mine life to 2025 at over 11,000 tons per day (tpd) with an average strip ratio of 0.88:1.
Moss Mine Location and Site Access Details
The Moss Mine is in the southern part of the basin-and-range topographic province in the Black Mountain Range about 16093.4m (10 miles) east of Bullhead City along the Silver Creek Road in Arizona.
Bullhead City is about 144841m (90 miles) southeast of Las Vegas, Nevada. The mine comprises approximately 16899.672 hectares (ha) (41,760 acres).
The mine is accessible via State Highway 68 from Bullhead and Kingman from the north, from Bullhead by Silver Creek Road (Country Route 10), and from south-central by Boundary Cone Road from Fort Mohave (Country Route 153).
The mine can also be reached from the Historic Route 66 connecting Golden Shores, Oatman, and Kingman from the south. Many ATV trails also surround the site.
The chartered flights from McCarran International Airport, Las Vegas to the Laughlin-Bullhead City Airport and the railway station of Needles, California can be used to reach the site.
Moss Mine Geology and Mineralisation
The Moss Mine is hosted by Moss porphyry. Moss porphyry is a monzonite to quartz monzonite porphyry intrusion.
The Moss porphyry is made up of coarse-grained plagioclase phenocrysts with lesser hornblende phenocrysts and biotite.
Towards west of the West Pit, the mineralisation is hosted in the Peach Springs tuff. The Peach Springs tuff is an intra-caldera fill interbedded with volcaniclastic sediments and megabreccia blocks.
The gold-silver mineralisation is hosted within three veins: the dominant Moss Vein, the western extension of the Moss Vein (West Vein), and the Ruth Vein towards the south of the Moss Vein.
In stockwork zones, the gold mineralisation occurs as visible quartz-calcite veinlets. The Moss Vein is highly fractured and hosts sulphide minerals.
The primary mineralisation of the mine comprises gold, silver, calcite, electrum in quartz, and electrum in/on pyrite grains. At deep depths, the mineralisation consists of heap-leach gold.
Moss Mine Reserves
The total (measured and indicated) mineral resource estimate of the mine is 42.83Mt containing 490.2koz gold at a grading of 0.011oz/ton and 5,754koz silver at a grading of 0.13oz/ton.
The inferred mineral resources are 7.23mt containing 73.8koz gold at a grading of 0.010oz/ton and 940koz silver at a grading of 0.13oz/ton.
At a gold cutoff grade of 0.006oz/ton, the proven mineral reserves of the mine are 5.08Mt containing 68.1koz gold at a grading of 0.013oz/ton and 858.8koz silver at a grading of 0.17oz/ton.
The probable mineral reserves are 8.96Mt containing 116.4koz gold at a grading of 0.013oz/ton and 1,342koz silver at a grading of 0.15oz/ton.
The total (proven and probable) mineral reserves of the mine are 14.04Mt containing 184.5koz gold at a grading of 0.013oz/ton and 2,200.8koz silver at a grading of 0.16oz/ton.
Mining and Ore Processing
The Moss Mine is mined using conventional open pit hard rock methods. The mining fleet includes 70-100t rigid frame haul trucks, front-end loaders, and excavators to load in areas facing dilution.
The extraction of gold and silver is done via heap leaching. The mined ores are crushed to P80 of 3/8 inch and mixed with pebble quick lime. They are then sent to heaps and stacked.
The leach pads are diluted with dilute sodium cyanide solution after stacking wherein silver and gold are dissolved as the solution moves through the leach pads.
From the leach pads, the pregnant solution enters the pregnant solution pond and passes through a Merrill-Crowe plant.
In the plant, gold and silver are precipitated out of the solution through zinc powder. The resultant precipitate undergoes filtration, drying, and smelting producing gold and silver doré bars.
Infrastructure
The Moss Mine consists of power infrastructure, a Merrill-Crowe plant, administrative and support offices, access roads, an existing assay laboratory, a 1,500 feet warehouse, and transport vehicles.
The water demand at the site is 225 gallons per minute (gpm) on an average. At peak, the demand ranges from 200-300gpm.
The mine receives power by a recently constructed approximately 17702.8m (11 miles) transmission line connecting Bullhead City and the mine site.
The 24.9kV power line was energised by Mohave Electrical Cooperative in September 2020. For backup, the mine used diesel generators. The 11104.5m (6.9 mile) long electrical system of the mine was financed with $2.1m.
Moss Mine Contractors
The Engineering Production and Construction (EPC) contract of the Moss Mine was awarded to M3 Engineering in August 2016.
The 2021 technical report of the mine was prepared by Independent Mining Consultants, Forte Dynamics, and Great Basin Environmental Services.
McCoy and Sons acts as the contract miner as per the 2021 technical report and Wesco handles production drilling and blasting works.
The electrical system of the mine was developed by Northern Vertex and Mohave Electric including construction and financing in April 2020.
N.A.D Degerstrom was selected for pond earthworks and leach pad advancement. Environmental Group focused on linear installations and the concrete pedestals for the eight Caterpillar generators and transformers were delivered by the Great Basin Industrial in 2017.
In the same year, the agglomeration circuit of the cement silo and agglomeration drum for the crushing plant was commissioned by WestPro Machinery.
Since September 2017, the clean drain rock for use as an over liner in leach pad was produced by Superstition Crushing.
The 2017 Preliminary Economic Analysis of Phase 3 of the project was prepared by M3 Engineering.
Goodfellow Crushers designed, fabricated, and delivered the three-stage crushing plant for the mine. The contract was awarded to Goodfellow in December 2016.
In December 2016, the civil works contract for the mine was awarded to N.A. Degerstrom. The contract scope included site earthworks, grading of site roads, power station, remediation of historic mine openings, laydown, storage areas, security/parking areas, and areas needed for future crusher and installations.
The 3,000m drilling contract was signed by Northern Vertex with BDW International in December 2016.
Golder Associates conducted site-geotechnical, geophysical, and hydrology field studies at the mine site. The feasibility study of the mine was prepared by M3 and Minefill Services in 2015.
The 2014 technical report of the mine was prepared by consultants: Minefill and Fladgate Exploration Consulting.
The metallurgical test work was conducted by Metcon Research. Metcon was selected by Patriot Gold between 2004 and 2009.
