This feasibility study updates metallurgical characterization and process design criteria for the Gold Bar Project, incorporating actual heap leach performance from Gold Bar North and new testwork on Gold Bar South.
Report context
This technical report, filed as a Form 43-101F1 feasibility study, documents the metallurgical and processing basis for the Gold Bar Project in Eureka County, Nevada, USA. The report updates the previous 2018 feasibility study, with the mineral resource statement effective December 1, 2020. The Gold Bar deposit is subdivided into Gold Bar North and Gold Bar South.
Processing route
Gold Bar North metallurgical background
Gold Bar North comprises three ore deposits: Pick (East and West), Ridge, and Cabin. Mineralization is similar across all three and occurs as a sediment-hosted gold deposit, mostly hosted in carbonate-rich sedimentary rocks of the Devonian McColley Canyon Formation, characterized by micron-sized gold and distinct hydrothermal alteration.
Most metallurgical samples supporting Gold Bar North recovery development were collected in 2010–2011 and reported in the Gold Bar PFS in October 2012. Additional drilling and metallurgical testing occurred between 2012 and 2017. Metallurgical characterization for Gold Bar North in the 2018 FS combined results from the 2012 PFS, 2014 bulk column testwork, 2015 bottle roll testing on RC drill samples, and 2017 column testwork.
Process design and actual leach performance
The 2018 feasibility study process plant design includes crushing to 100% minus 6-inch and agglomeration of the minus 3-inch fraction, with the leach pad loaded after recombining the fractions.
Actual leaching at Gold Bar North began in December 2018. Recovery projections in this report have been updated based on operational differences resulting from an increased percentage of run-of-mine (ROM) ores and elevated clay content in the placed ore negatively impacting the leaching hydrodynamics.
Gold Bar South metallurgical characterization
The Gold Bar South deposit's metallurgical characterization has been preliminarily developed and is limited to bottle roll test results completed between 2008 and 2011, column testing, and cyanide digestion gold assays from several drilling programs throughout the project history. Column testing of material from a 2019 drilling campaign has recently been completed.
Available results indicate that Gold Bar South ore is oxidized and amenable to cyanidation. About 75% of the Gold Bar South resource is hosted in the Webb Formation, with the remainder hosted in the underlying Devils Gate Formation.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Crushing product size | 100% minus 6-inch | Process design |
| Agglomeration feed fraction | Minus 3-inch | Process design |
| Gold Bar North leach start | December 2018 | Actual operating data |
| Gold Bar South host rock, Webb Formation | ~75% of resource | Geological estimate |
| Gold Bar South host rock, Devils Gate Formation | ~25% of resource | Geological estimate |
| Gold Bar South cyanidation amenability | Oxidized and amenable | Bottle roll and column testwork |
Project website: https://www.mcewenmining.com/operations/gold-bar-project/default.aspx
Technical qualifications
Metallurgical characterization for Gold Bar South is preliminary and limited to historical bottle roll results (2008–2011), column testing, and cyanide digestion gold assays. Recovery projections for Gold Bar North incorporate operational changes from design assumptions, specifically increased ROM ore percentage and elevated clay content affecting leach hydrodynamics.
Source: Gold Bar Project Form 43-101F1 Technical Report – Feasibility Study, section 13 Mineral Processing and Metallurgical Testing.
