Overview
Stage | Production |
Mine Type | Underground |
Commodities |
|
Mining Method |
- Longhole open stoping
- Paste backfill
|
Processing |
- Gravity separation
- Concentrate leach
- Agitated tank (VAT) leaching
- Carbon in leach (CIL)
- AARL elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
|
On-Site Camp |
yes |
Mine Life | 2031 |
St Barbara approved the project to extend the historic Gwalia gold mine to at least 2000 metres below surface in March 2017. The $100 million project, which remained on track after the December 2018 quarter, is expected to take up to three years to complete. It consists of two main components, a ventilation upgrade and paste aggregate fill. St Barbara has forecast Gwalia to produce 290,000 ounces of gold a year by the 2022 financial year. |
Latest News | St Barbara cuts gold production outlook at Gwalia March 22, 2019 |
Source:
p.19
Summary:
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 2,080m below surface and remains open.
Mining Methods
- Longhole open stoping
- Paste backfill
Source:
p.2
Summary:
The primary mining method since resumption of underground production in 2008 is a Longhole Open Stoping method with paste fill. Stoping configurations are predominantly double lift (40m vertical interval) however single lift stoping (20m vertical interval) is used in some areas. The Double Lift stoping method involves concurrently mining the uphole and downhole sections of the stope. The upper and lower portions of the stope are drawn back and bogged at the same time.
Source:
p.4
Processing
- Gravity separation
- Concentrate leach
- Agitated tank (VAT) leaching
- Carbon in leach (CIL)
- AARL elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Flow Sheet:
Summary:
All Gwalia 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 and hybrid CIL circuit with one designated leach tank and 7 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 (Zimmerman 2013). Gold doré bars are transported by armoured trucks to the Perth Mint for refining.
Recoveries & Grades:
Commodity | Parameter | 2019 | 2018 | 2017 | 2016 |
Gold
|
Recovery Rate, %
| 98 | 98 | 97 | 96 |
Gold
|
Head Grade, g/t
| 10.8 | 12 | 10.7 | 9.3 |
Production:
Commodity | Units | 2020 | 2019 | 2018 | 2017 | 2016 |
Gold
|
oz
| 182 ^ | 220,169 | 268,428 | 265,057 | 267,166 |
All production numbers are expressed as metal in doré.
^ Guidance / Forecast.
Operational Metrics:
Metrics | 2019 | 2018 | 2017 | 2016 |
Ore tonnes mined
| 625 kt | 679 kt | 790 kt | 924 kt |
Tonnes milled
| 652 kt | 711 kt | 828 kt | 951 kt |
Reserves at June 30, 2019:
Category | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
2,220 kt
|
Gold
|
8 g/t
|
568 koz
|
Probable
|
7,915 kt
|
Gold
|
5.9 g/t
|
1,506 koz
|
Proven & Probable
|
10,135 kt
|
Gold
|
6.4 g/t
|
2,073 koz
|
Measured
|
5,034 kt
|
Gold
|
7.3 g/t
|
1,183 koz
|
Indicated
|
17,527 kt
|
Gold
|
6 g/t
|
3,393 koz
|
Inferred
|
1,129 kt
|
Gold
|
5.5 g/t
|
199 koz
|
Total Resource
|
23,690 kt
|
Gold
|
6.3 g/t
|
4,775 koz
|
Commodity Production Costs:
| Commodity | Units | 2020 | 2019 | 2018 | 2017 | 2016 |
Credits (by-product)
|
Gold
|
AUD
|
|
-2 / oz
|
-2 / oz
|
|
|
Cash costs
|
Gold
|
AUD
|
|
703 / oz
|
572 / oz
|
|
|
Total cash costs
|
Gold
|
AUD
|
|
746 / oz†
|
613 / oz†
|
592 / oz†
|
609 / oz†
|
All-in sustaining costs (AISC)
|
Gold
|
AUD
|
1,260 / oz ^†
|
1,027 / oz†
|
802 / oz†
|
785 / oz†
|
783 / oz†
|
^ Guidance / Forecast.
† Net of By-Product.
Financials:
| Units | 2020 | 2019 | 2018 | 2017 | 2016 |
Capital expenditures (planned)
|
M AUD
| 92.5 | | | | |
Revenue
|
M AUD
| | 392.68 | 461.26 | 441.95 | 440.33 |
Mine Management:
Job Title | Name | Profile | Ref. Date |
Environmental Superintendent
|
Dan Pintea
|
|
Jan 16, 2020
|
Technical Services Manager
|
Andrew Shepherd
|
|
Jan 16, 2020
|
Corporate Filings & Presentations:
News: