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Australia
Leonora Operations - Gwalia Mine

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 Location:
3 km S from Leonora, Western Australia, Australia

  Address:
Kane Street, Gwalia
PO Box 67
Leonora
Western Australia, Australia
6438
Phone  ...  Subscription required
Fax+61-(8)-9037-6988
WebsiteWeb
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Fleet
  • Personnel
  • Filings & News

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Overview

StageProduction
Mine TypeUnderground
Commodities
  • Gold
Mining Method
  • Longhole open stoping
  • Paste backfill
Processing
  • Gravity separation
  • Centrifugal concentrator
  • Carbon re-activation kiln
  • ACACIA reactor
  • Smelting
  • Agitated tank (VAT) leaching
  • Concentrate leach
  • Carbon in leach (CIL)
  • AARL elution
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)
Mine Life2031
The cornerstone of Leonora Operations, Gwalia mine, is the deepest underground trucking mine in Australia. Its depth is over 1,600 metres below surface.
Latest NewsSt Barbara sets sights on new open pit at Leonora     October 25, 2021


Owners

Source: p. 8
CompanyInterestOwnership
St Barbara Ltd. 100 % Direct
Gwalia Mine is 100% owned by St Barbara Limited.

Deposit Type

  • Vein / narrow vein


Summary:

Gold mineralisation occurs as a number of en echelon, moderately east dipping foliation parallel lodes within strongly potassic altered mafic rocks and extends over a strike length of approximately 500 m and to a vertical depth of at least 2,300 m. Four primary lodes (Main Lode, South West Branch, South Gwalia Series and West Lode) have been identified and the geometries summarised below.

Mineralisation domains are defined by abundance of quartz and quartz/carbonate veining, the presence of distinctive laminated veining (quartz/sericite/sulphides +/- au), strong potassic alteration, abundance of sulphides (commonly >3% pyrite) and elevated gold grade (>0.5g/t).

The mineralised zone strikes 15 degrees east of true north over a distance of 500m and plunges 45 degrees to the southeast. The mineralised zone consists of several stepped or en echelon style foliation parallel lodes disposed in plan in a “horse-shoe” shape with the limbs converging at the southern end. The mineralised zone and individual lodes dip east at 35 to 45 degrees and are conformable with the foliation of the Mine Sequence mafic schists. Individual lode widths vary from 2m to 30m true width. Mineralisation has been tested to approximately 2,300m below surface and remains open.


Mining Methods

  • Longhole open stoping
  • Paste backfill


Summary:

St Barbara’s Leonora Operations comprise almost 300 square kilometres of mineral tenure and consists of the Gwalia underground mine and 1.2 Mtpa processing plant, as well as nearby development opportunities as:
- Gwalia open pit mineralisation between 280 and 500 metres below surface(mbs) was identified as a potential source of open pit mill feed upon completion of underground mining.

- The Harbour Lights Deposit is located approximately 5 kilometres from the Leonora Processing Facility. The deposit was initially mined by underground methods between 1904 and 1935 via a series of shafts to around 40 mbs. More recently, ore was extracted from an open pit by Harbour Lights Mining between 1985 and 1992. Since 1995, mining is not undertaken.

- Tower Hill is located approximately 2 km north of the Leonora Processing Facility. Intermittent mining has occurred in the vicinity of Tower Hill since 1898. Early mining was from a small open cut and underground mine to 66 metres depth. The existing Mineral Resources and Ore Reserves for Tower Hill will remain in place while work continues on the best extraction and processing options for this mineralisation.

- The Jasper Region comprises a series of historic open pits and prospects approximately 25 km north of Gwalia. These include the Jasper Flat, Jasper Hill, Falklands Trend, Hawaii, Greenland and Trevor Bore deposits.

St Barbara’s flagship mine Gwalia is located 3 kilometres south of the Leonora Township. Gold has been extracted from the deposit over time by both open pit and underground methods.

Currently reported Mineral Resources start at approximately 1,100 mbs and extend to depth and are referred to as Gwalia Deeps. The extent of past production within the mine itself was determined by the prevailing gold price at the time and was also a function of the distance from the original shaft access. In particular as the Gwalia Mineral Resource contains four main lode systems (Main Lode, South West Branch, South Gwalia Series and West Lode) there are areas within the mine where only some lodes have been developed and others have been left untouched.

Gwalia is the deepest underground trucking mine in Australia, that employed long hole open stoping with paste backfill.

Having added 1.4 Moz of gold to the Mineral Resource base through Gwalia Open Pit and Harbour Lights and with aspirations to add a further 1.1 Moz of gold from Gwalia and the Jasper Region the next step is to progress studies to convert this material into Ore Reserves and bring it into the life of mine plan.


Crushing and Grinding
Flow Sheet: Source
Crusher / Mill TypeModelSizePowerQuantity
Jaw crusher 1
Cone crusher 2
Ball mill 1

Summary:

All Gwalia mine ore is trucked to the Gwalia processing plant. The processing plant is located at St Barbara’s Leonora Operations and consists of a three-stage crushing circuit, single-stage milling circuit.


Processing

  • Gravity separation
  • Centrifugal concentrator
  • Carbon re-activation kiln
  • ACACIA reactor
  • Smelting
  • Agitated tank (VAT) leaching
  • Concentrate leach
  • Carbon in leach (CIL)
  • AARL elution
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)

Flow Sheet: Subscription required

Summary:

Gwalia processing plant consists of a three-stage crushing circuit, single-stage milling circuit and hybrid carbon-in-leach circuit with one designated leach tank and seven adsorption tanks. Gold is recovered from activated carbon into concentrated solution via a split AARL-type elution circuit. Electrowinning and smelting are conducted in an adjacent secure gold room. The tailings from the process are thickened and pumped to a paddock-type tailings storage facility with multi-spigot distribution. Gold doré bars are transported to the Perth Mint for refining.

The technology associated with processing of Gwalia ore is currently in operation and is based on industry standard practices.

Metallurgical recovery is modelled based on the observed relationship between head grade and recovery. The average of the modelled metallurgical recovery over the Ore Reserve mine plan is 96.8%.

Recoveries & Grades:

CommodityParameter20212020201920182017
Gold Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required9897
Gold Head Grade, g/t  ......  Subscription required  ......  Subscription required  ......  Subscription required12.510.7

Production:

CommodityUnits2022202120202019201820172016
Gold koz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required  ......  Subscription required268265276
All production numbers are expressed as metal in doré. ^ Guidance / Forecast.
Subscription required - Subscription is required.

Operational Metrics:

Metrics202120202019201820172016
Ore tonnes mined  ......  Subscription required  ......  Subscription required625 kt679 kt790 kt924 kt
Waste  ......  Subscription required  ......  Subscription required
Tonnes milled  ......  Subscription required  ......  Subscription required652 kt711 kt828 kt1,027 kt
Plant annual capacity  ......  Subscription required  ......  Subscription required1.4 Mt
Subscription required - Subscription is required.

Reserves at June 30, 2021:
Ore Reserves Cut-off Grades: Gwalia (4.0 g/t Au), Tower Hill (2.8 g/t Au).
Mineral Resources Cut-off Grades: Gwalia (2.5 g/t Au), Gwalia Open Pit (0.4 g/t Au), Harbour Lights (0.4 g/t Au Oxide / 0.8 g/t Au Sulphide), Tower Hill (2.5 g/t Au).

CategoryTonnage CommodityGradeContained Metal
Proven & Probable 15,880 kt Gold 4.9 g/t 2,527 koz
Total Resource 51,864 kt Gold 4.1 g/t 6,804 koz

Commodity Production Costs:

CommodityUnits2021202020192018
Credits (by-product) Gold AUD  ......  Subscription required  ......  Subscription required  ......  Subscription required -2 / oz
Cash costs Gold AUD  ......  Subscription required  ......  Subscription required  ......  Subscription required 572 / oz
Total cash costs Gold AUD  ......  Subscription required†  ......  Subscription required†  ......  Subscription required† 613 / oz†
All-in sustaining costs (AISC) Gold AUD  ......  Subscription required†  ......  Subscription required†  ......  Subscription required† 802 / oz†
^ Guidance / Forecast.
† Net of By-Product.
Subscription required - Subscription is required.

Financials:

Units2022202120202019201820172016
Capital expenditures (planned) M AUD  ......  Subscription required
Growth Capital M AUD  ......  Subscription required  ......  Subscription required  ......  Subscription required
Sustaining costs M AUD  ......  Subscription required  ......  Subscription required  ......  Subscription required33.8   30.2   27.1  
Capital expenditures M AUD  ......  Subscription required  ......  Subscription required  ......  Subscription required70.6   -47.5   36.1  
Revenue M AUD  ......  Subscription required  ......  Subscription required  ......  Subscription required461.3   441.9   440.3  
Gross profit M AUD  ......  Subscription required  ......  Subscription required  ......  Subscription required303.3   298.8   279.2  
Pre-tax Income M AUD  ......  Subscription required  ......  Subscription required  ......  Subscription required
EBITDA M AUD  ......  Subscription required  ......  Subscription required  ......  Subscription required285.2   281.5  
Subscription required - Subscription is required


Heavy Mobile Equipment as of August 9, 2018:
HME TypeModelSizeQuantity
Drill (long hole) ....................... Subscription required
Jumbo ....................... Subscription required
Loader ....................... Subscription required
Truck (underground) ....................... Subscription required 65 t ....................... Subscription required
Truck (underground) ....................... Subscription required 60 t ....................... Subscription required
Truck (underground) ....................... Subscription required 65 t ....................... Subscription required
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Oct 6, 2021
....................... Subscription required ....................... Subscription required Subscription required Oct 6, 2021
....................... Subscription required ....................... Subscription required Subscription required Oct 6, 2021
....................... Subscription required ....................... Subscription required Subscription required Oct 6, 2021
....................... Subscription required ....................... Subscription required Subscription required Oct 6, 2021
Subscription required - Subscription is required.

Staff:

EmployeesContractorsYear
Subscription required Subscription required 2021
Subscription required Subscription required 2020

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
Annual Report 2018
Corporate Presentation 2018
Quarterly Report 2018
Annual Report 2017
Year-end Mineral Reserves 2016
Project Description 2013
Subscription required - Subscription is required.

News:

NewsDate
St Barbara sets sights on new open pit at Leonora October 25, 2021
St Barbara looks to fill the mill to uplift Leonora September 13, 2021
St Barbara builds foundation for Gwalia future April 28, 2021
St Barbara puts Gwalia in the hands of Macmahon March 3, 2021
St Barbara prepares Gwalia comeback February 17, 2021
St Barbara cuts gold production outlook at Gwalia March 22, 2019

Aerial view:

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