Castle Mountain - Phase 2

Long-life low-cost gold mine in California

Castle Mountain Phase 2 operations would increase production to on average 200,000 oz of gold per year, with a small mill to process high-grade material and ROM heap leaching of lower-grade ore.

development strategy

On September 17, 2020, Equinox Gold announced the commencement of Phase 1 operations for Castle Mountain. The project is being developed in a phased ramp-up scenario, starting with run-of-mine heap leaching of stockpile material using existing operating permits, and then the potential for a second phase expansion that will include milling of higher-grade ore.


Mine type Open pit
Access Paved roads, 120 km south of Las Vegas
Strategy Phase 1: Initial ROM heap leach of stockpile material
Phase 2: Expansion with ROM heap leach and milling of higher grade ore
Production target Phase 1: ~40,000 oz/year
Phase 2: 203,000 oz/year
Reserves P&P: 3.6 Moz @ 0.56 g/t gold
Resources M&I: 4.3 Moz @ 0.56 g/t gold (inclusive)
Inf: 2.2 Moz @ 0.40 g/t gold
Status Prefeasibility completed in July 2018
Phase 1 operations started in September 2020



The Castle Mountain Gold Mine produced more than one million ounces of gold as an open-pit heap-leach mine from 1992 to 2004, when the mine was shut down due to low gold prices. Material below 0.50 g/t gold mined from the Oro Belle and Jumbo pits was placed into the JSLA pit.

Higher gold prices justify putting the mine back into production to process that stockpile material, which is economic using current gold prices. Recent drilling, aimed at upgrading material previously classified as waste or inferred resources within and adjacent to the pit shells, has discovered consistently good grades and also some higher-grade intercepts. Drilling has also discovered higher-grade mineralization below the backfill material, including a new zone of mineralization in the andesite footwall, which was previously thought to be unmineralized.


Phased Ramp-up

To access existing and potentially new resources, Equinox Gold intends to recommence production in a phased ramp-up scenario, as outlined below. Based on the July 2018 prefeasibility study, at $1,250/oz gold the project has a net present value (discounted at 5%) of US$406 million.

Phase 1

  • Re-establish onsite operations using the current permit 
  • Initial mining and run-of-mine (“ROM”) heap leach processing of the historical JSLA pit stockpile material
  • Production target: ~40,000 oz/year 
  • Construction requirements: Construct small leach pad and gold recovery plant
  • Timeline: Production commenced in Q4-2020

Phase 2

  • Feasibility study targeted for Q1-2021
  • Higher throughput with milling of higher-grade ore and ROM heap of lower-grade material 
  • Production target: ~200,000 oz/year
  • Permit requirements: New Environmental Impact Assessment and expansion permit
  • Water requirements: Source additional water for increased throughput


On July 16, 2018, Equinox Gold released the results of a prefeasibility study for the Castle Mountain Gold Mine in California, USA. The prefeasibility contemplates developing the project in a phased ramp-up scenario. Phase 1 would be developed as an open-pit run-of-mine (“ROM”) heap leach mine leaching stockpile material from previous operations. Phase 2 would include milling of a limited stream of higher-grade material and ROM leaching of the balance. With 3.6 million oz of gold reserves, Castle Mountain would be a robust, low-cost gold mine producing 2.8 million ounces of gold over a 16-year mine life. 

Download the Prefeasibility Study Technical Report, or download the slide deck discussing the results.

2018 Prefeasibility Study Highlights (US$)

Gold price (base case) $1,250/oz
P&P Reserve 3.6 Moz Au @ 0.56 g/t Au
M&I Resource (inclusive of reserves) 4.3 Moz Au @ 0.56 g/t Au
Mine Life 16 years
Phase 1 production (yrs 1-3)
Phase 2 production (yrs 4-16)
Avg. 45 koz gold
Avg. 203 koz gold
Strip Ratio / Recovery 3.6 / 79%
Total Production (LOM) 2.8 Moz gold
Initial Capex
Phase 1
    Phase 2

Phase 1 $58 M 
Phase 2 $175 M + Fleet
Sustaining Capex $142 M 
Cash Cost (LOM) $712/oz
AISC (LOM) $763/oz
Cash Flow (after tax) (LOM) $865 M (net of initial capital)
NPV 5% (after tax) $406 M ($534 M at $1,350/oz gold)
IRR (after tax) 20% (25% at $1,350/oz gold)

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