Tonopah West Silver-Gold Project is located in the US state of Nevada within one of the largest historic silver districts in North America.
The project is being developed by junior precious metal focused exploration company Blackrock Silver.
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The company announced a positive Preliminary Economic Assessment (PEA) for the Tonopah West Project in September 2024.
According to the PEA, the mine is expected to deliver 424,000 payable gold ounces and approximately 31.8 million payable silver ounces over an eight-year life of mine (LOM).
The report estimated that the property will generate $496m after-tax LOM cash flow. The project also holds significant potentiality for expansion.
The development of Tonopah West is expected to entail an initial capital expenditure of $177.8m, including $22.3m in contingency costs. It would require an additional $178m as sustaining capital for underground mining development and other works.
Tonopah West Project Location
The Tonopah West property is located in the Walker Lane trend of Western Nevada, adjacent to the town of Tonopah.
Overall, the site includes 1,030.2 hectares of private land (patented mining claims) and Department of the Interior Bureau of Land Management-controlled public land. It includes 83 unpatented lode mining claims and 100 patented claims held by Blackrock.
The resource area is situated within patented mining claims.
Background
Historical mining and exploration activities in the area can be traced back to early 1900s.
Tonopah Silver District already produced more than 174 million ounces of silver and 1.8 million ounces of gold from approximately 7.5 million tonnes of ore.
Modern exploration activity commenced in 1969 by Howard Hughes’ Summa Corporation. Subsequent operators included Houston Oil and Minerals, Chevron USA (Chevron), Coeur Mining and Eastfield Resources.
Blackrock acquired an option on the Tonopah West property in 2020. In 2024, the company exercised the option to buy the property.
Geology and Mineralisation
The Tonopah West project is located in the western part of the Tonopah mining district.
Surface exposures at the property were observed to include Miocene volcanic rocks and Quaternary fan and pediment deposits. At depth, it features the andesitic to silicic volcanic flows, tuffs, and volcaniclastic rocks of the Tonopah volcanic centre above basement granitic intrusive rocks.
The project hosts silver-gold mineralisation in low- to intermediate-sulfidation epithermal quartz veins and quartz-cemented breccias under the surface.
The veins run west, west-northwest or northwest dipping towards the north and northeast. Average thickness of the modelled veins is 4.3m.
The principal host rocks are West End Rhyolite and also Mizpah Andesite, Extension Breccia, Tonopah Formation, and Sandgrass Andesite.
Tonopah West Project Mineral Resource Estimate
Tonopah West Project’s Mineral Resource Estimate (MRE) contains Inferred Resources of 6.35 million tonnes grading 2.82 grams per tonne (g/t) gold (Au) and 237.8 g/t silver (Ag) totalling 577,000 ounces of gold and 48.5 million ounces of silver.
At 492.5 g/t AgEq grade, the figure represents a total of 100.56 million AgEq ounces.
Mining and Recovery
The silver-gold project comprises multiple steeply and moderately-dipping vein structures.
According to the PEA, narrow high-grade veins will be mined by Longitudinal Open Stoping and overhand Cut-and Fill methods.
Cut-and-Fill mining will involve making an initial cut inside the mineralisation low in the vein, followed by backfilling. The filled stopes will be then used as platform to extract ore in a bottom-up manner.
Longitudinal Open Stope (longhole stoping) methods will be used to mine wider veins.
Tonopah West Project is expected to have a processing plant that can treat 1,500 metric tonnes per day.
Gold and silver will be extracted from the crushed and finely ground whole mineral via agitated cyanide leaching to produce a pregnant leach solution.
The solution is then separated from the solid material in counter-current decantation thickeners.
Merrill-Crowe zinc precipitation will be used to recover metal values, followed by precipitate smelting to produce gold and silver doré bars.
The PEA considers dewatering process tailings by pressure filtration, while solid tailings waste material will be separated via pressure filtration and then transported by dump truck to a lined dry-stack tailings storage area.
Contractor Involved
The Tonopah West Project PEA was prepared by Minetech.
