• Operations

Costerfield Mine

Property At A Glance

Victoria, Australia
Land Package
1,219 hectares
Mining Method
Long-hole stoping with cemented rock fill
Gold and Antimony
2022 Production
64,659 AuEq oz (47,887 Au oz & 2,292 Sb t)
Life of Mine
5 years
Processing Capacity
150,000 tonnes per annum

2023 Outlook

Gold (oz)
44,000 – 49,000
Antimony (t)
1,800 – 2,400
Gold Equivalent (oz)(1)
56,000 – 64,000
Cash Costs ($USD/oz)(2)
$650 – $825
All-in sustaining Costs ($USD/oz)(2,3)
$925 – $1,075
Capital Expenditures ($USDM)(4)
$20M – $24M
  • Notes
    • Cash cost and all-in sustaining costs are non-IFRS measures.
    • See “Non-IFRS Measures” in our MD&A.
    • Assumes average metal prices of: Au $1,797/oz, Sb $10,805/t 
    • Consolidated all-in sustaining costs per Au Eq. oz includes corporate overhead spending.

2022 Performance

Gold (oz)
Antimony (t)
Gold Equivalent (oz)
Cash Costs ($USD/oz)
All-in sustaining cost ($USD/oz)
Capital Expenditures ($USDM)
  • Read more on Geology and Mineralization

    Veins at Costerfield typically comprise quartz (laminated to brecciated) and sulphides. The dominant sulphide mineral is stibnite (Sb2S3). In addition to stibnite, arsenopyrite and pyrite occur in minor amounts.

    The veins occur within discrete shear systems. The following paragenesis has been interpreted:

    • sericitization of host rock sediments with minor pyrite deposition;
    • faulting with associated open-space deposition of quartz, locally with coarse gold, and partial replacement of pyrite by auriferous arsenopyrite – only minor replacement of sericite-altered host rock by quartz occurs, with some remobilization of sericite into convoluted cross-cutting veinlets;
    • open-space deposition of carbonate in quartz vugs;
    • influx of Sb-rich solutions, resulting in massive stibnite infill and replacement of brecciated quartz-carbonate veins. The massive stibnite contains finely-disseminated Au; and
    • re-crystallization / annealing of stibnite.

    Ore shoots in the veins are typically 0.25 – 1.0 m thick and extend for 200 m or more along strike. They are typically displaced by flat faults so that they appear flat-bottomed. However, as with the Cuffley Lode, the Company is having success finding the offset parts of ore shoots below the flat faults; the deepest intercept in the district, approximately 500 m below surface in the Cuffley Lode, is also one of the highest-grade intercepts.

    The Brunswick vein lies approximately 600 m northwest of the northernmost point of the Cuffley Lode.  The lode is sub-vertical and occurs over a strike length of approximately 450 m, with a down-dip extent of approximately 200 m and an average true thickness of approximately 1.28 m. Exploration drilling has identified mineralization to the south and at depth below the known Brunswick Lode. Mineralization is broken into two zones of mineralization below the Brunswick Lode, called the P-K domain and Brunswick Deeps. The P-K domain is capped by the shallow west-dipping Penguin Fault, and extends to the Kiwi Fault. The Brunswick Deeps zone is defined by the west-dipping Kiwi Fault and Adder Fault. Similar in nature to Cuffley and N-Lodes, the mineralization in the two domains is generally confined to sub-vertical quartz–stibnite veins.

    The Youle deposit extends below the historical Costerfield, Minerva and Bombay group of mines located approximately 1.2 km northeast of Brunswick. Mineralization was identified in 2011, in drill hole MB012, which struck the down-dip continuation of the vertical Kendall Lode, offset westward over the west-dipping No. 3 thrust fault. In 2016, drill hole BC006W1 revealed the existence of a high-grade north–northwest striking, west-dipping lode structure, Youle. The Youle Lode dips at a shallower angle to the mineralized lodes in Augusta and Cuffley and has been identified as the down-dip continuation of the vertical Kendall Lode offset westward over the west-dipping No.5 thrust fault.

    Youle has thus far demonstrated consistent structural and grade continuity over much of its extent. The Youle Lode has a strike length of 600 m (width of 150 m) and ranges in true thickness between 0.16 m and 1.37 m.  Similar to the Augusta and Brunswick Lodes, mineralization is confined to quartz‑stibnite veins.

  • Notes

    1.    Mineral Reserve estimated as of December 31, 2021, and depleted for production through to December 31, 2021.
    2.    Tonnes are rounded to the nearest thousand; contained Au (oz) is rounded to the nearest thousand; contained Sb (t) rounded to nearest hundred.  
    3.    Totals may appear different from the sum of their components due to rounding.
    4.    Lodes have been diluted to a minimum mining width of 1.5 m for stoping and 1.8 m for ore development. 
    5.    A 3.8 g/t AuEq cut-off grade is applied.
    6.    Commodity prices applied are Au price of USD1,500/oz, Sb price of USD7,500/t and exchange rate USD:AUD of 0.71.
    7.    The (AuEq) is calculated using the formula: AuEq = Au g/t + 1.06 * Sb %.
    8.    The Mineral Reserve is a subset, a Measured and Indicated only Schedule, of a Life of Mine Plan that includes mining of Measured, Indicated and Inferred Resources.
    9.    The Mineral Reserve Estimate was prepared by Dylan Goldhahn, AusIMM under the direction of Daniel Fitzpatrick, MAusIMM, who are both full time employees of Mandalay Resources. The Mineral Reserve estimate was independently verified by Aaron Spong FAusIMM CP (Min) who is a full-time employee of Mining Plus. Mr Spong fulfils the requirements to be a "Qualified Person" for the purposes of NI 43-101, and is the Qualified Person under NI 43-101 for the Mineral Reserve. 

  • Notes

    1.    The Mineral Resource is estimated as of December 31, 2021 with depletion through to this date.
    2.    The Mineral Resource is stated according to CIM guidelines and include Mineral Reserves.
    3.    Tonnes are rounded to the nearest thousand; contained Au (oz) is rounded to the nearest thousand; contained Sb (t) is rounded to nearest hundred.
    4.    Totals may appear different from the sum of their components due to rounding.
    5.    3.0 g/t AuEq cut-off grade over a minimum mining width of 1.2 m is applied where AuEq is calculated using the formula: AuEq = Au g/t + 1.58 * Sb %
    6.    The AuEq factor of 1.58 is calculated at a Au price of $1,700/oz, an Sb price of $8,500/t, and 2021 total year metal recoveries of 93% for Au and 95% for Sb.
    7.    Veins were diluted to a minimum mining width of 1.2m before applying the cut-off grade and peripheral mineralisation far from current development was excluded to comply with the Reasonable Prospects for Eventual Economic Extraction (RPEEE) criteria.
    8.    The Stockpile Mineral Resource is estimated based upon surveyed volumes supplemented by production data.
    9.    Geological modelling, sample compositing and Mineral Resource Estimation for updated models was performed by Joshua Greene, MAusIMM, a full-time employee of Mandalay Resources. 
    10.    The Mineral Resource Estimate was independently reviewed and verified by Dr Andrew Fowler MAusIMM CP (Geo), a full time employee of Mining Plus. Dr Fowler fulfils the requirements to be a "Qualified Person" for the purposes of NI 43-101, and is the Qualified Person under NI 43-101 for the Mineral Resource Estimate. 

2022 NI 43-101
2021 NI 43-101
2020 NI 43-101

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