• Operations

Costerfield Mine

Property At A Glance

Victoria, Australia
Land Package
1,293 hectares
Mining Method
Long-hole stoping with cemented rock fill
Gold and Antimony
2019 Production
15,258 gold ounce & 2,032 antimony tonnes
Life of Mine
3 – 4 years
Processing Capacity
150,000 tonnes per annum

2020 Outlook

Gold (oz)
32,000 – 38,000
Antimony (t)
3,000 – 3,500
Gold Equivalent (oz)(1)
44,000 – 52,000
Cash Costs ($USD/oz)(2)
$725 – $875
All-in sustaining Costs ($USD/oz)(2,3)
$1,010 – $1,220
Capital Expenditures ($USDM)(4)
$17M – $21M
  • Notes
    • Assumes metal prices of: $1,478/oz, Sb $5,931/t. Consolidated costs per Au Eq. oz includes corporate overhead spending and total care and maintenance costs at Cerro Bayo
    • Cash and all-in sustaining costs are a non-IFRS measure
    • Consolidated all-in sustaining cost guidance includes expected corporate overhead spending and care and maintenance costs
    • Capital expenditures includes exploration at Björkdal and Costerfield; consolidated cost guidance includes expected Corporate G&A

2019 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
    • Mineral Reserve estimated as of December 31, 2019
    • Tonnes are rounded to the nearest thousand; contained gold (oz) rounded to the nearest thousand and contained antimony (t) rounded to the nearest hundred. 
    • Totals may appear different from the sum of their components due to rounding.
    • Lodes have been diluted to a minimum mining width of 1.5 m for stoping and 1.8 m for ore development.
    • A 4.0 g/t Au Equivalent (AuEq) cut-off grade is applied.
    • Commodity prices applied are; gold price of $1,300/oz, antimony price of $7,000/t and exchange rate USD:AUD of 0.70.
    • AuEq value is calculated using the formula: AuEq = Au g/t + 1.28 * Sb %.
    • The Mineral Reserve is a subset, a Measured and Indicated only Schedule, of a Life of Mine Plan that includes mining of Measured and Indicated Resources.
    • The Mineral Reserve estimate was prepared by Daniel Fitzpatrick and Dylan Goldhahn, AAusIMM who are full time employees of Mandalay Resources and was independently verified by Anne-Marie Ebbels, MAusIMM, CP (Mining) who is a full time employee of SRK Consulting who is a qualified person under NI 43-101.
  • Notes
    • Mineral Resources estimated as of December 31, 2019, with depletion through to this date.
    • Mineral Resources stated according to CIM guidelines and include Mineral Reserves.
    • Tonnes are rounded to the nearest thousand; contained gold (oz) rounded to the nearest thousand and contained antimony (t) rounded to the nearest hundred. 
    • Totals may appear different from the sum of their components due to rounding.
    • A 3.5 g/t Au Equivalent (AuEq) cut-off grade over a minimum mining width of 1.2 m is applied where AuEq is calculated at a gold price of USD1,500/oz, antimony price of USD10,000/t.
    • The Au Equivalent value (AuEq) is calculated using the formula: AuEq = Au g/t + 1.52 * Sb %
    • Geological modelling and sample compositing was performed by Mandalay Resources and Cael Gniel MAIG, full time employee of Mining Plus. The models were independently verified by Danny Kentwell FAusIMM, full time employee of SRK Consulting.
    • The Mineral Resource estimation was performed by Cael Gniel. The resource models were verified by Danny Kentwell. Danny Kentwell is the qualified person under NI 43-101 and is responsible for the Resource estimate.

2020 NI 43-101