Overview
Stage | Production |
Mine Type | Underground |
Commodities |
|
Mining Method |
- Open stoping
- Bench stoping
- Avoca
- Uppers Retreat
- Cemented backfill
|
Processing |
- Agitated tank (VAT) leaching
- Carbon in pulp (CIP)
- Elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
|
Mine Life | 2023 |
Latest News | Aeris plots Cracow life extension through exploration July 2, 2020 |
Deposit Type
- Epithermal
- Breccia pipe / Stockwork
Summary:
The Cracow project area gold deposits are in the Lower Permian Camboon Andesite on the south eastern flank of the Bowen Basin. The regional strike is north-northwest and the dip 20° west southwest. The Camboon Andesite consists of andesitic and basaltic lava, with agglomerate, tuff and some inter-bedded trachytic volcanics. The andesitic lavas are typically porphyritic, with phenocrysts of plagioclase feldspar (oligocalse or andesine) and less commonly augite. To the west, the Camboon Andesite is overlain with an interpreted disconformity by fossiliferous limestone of the Buffel Formation. It is unconformably underlain to the east by the Torsdale Beds, which consist of rhyolitic and dacitic lavas and pyroclastics with inter-bedded trachytic and andesitic volcanics, sandstone, siltstone, and conglomerate.
Mineralisation is hosted in steeply dipping low sulphidation epithermal veins. These veins found as discrete and as stockwork and are composed of quartz, carbonate and adularia, with varying percentages of each mineral. Vein textures include banding (colloform, crustiform, cockade, moss), breccia channels and massive quartz, and indicate depth within the epithermal system. Sulphide percentage in the veins are generally low (<3%) primarily composed of pyrite, with minor occurrences of hessite, sphalerite and galena. Rare chalcopyrite, arsenopyrite and bornite can also be found.
Alteration of the country rock can be extensive and zone from the central veined structure. This alteration consists of silicification, phyllic alteration (silica, sericite and other clay minerals) and argillic alteration in the inner zone, grading outwards to potassic (adularia) then an outer propylitic zone. Gold is very fined grained and found predominantly as electrum but less common within clots of pyrite.
Mining Methods
- Open stoping
- Bench stoping
- Avoca
- Uppers Retreat
- Cemented backfill
Summary:
Underground mining is by owner-miner. Multiple underground orebodies are accessed by a singular decline to surface employing truck haulage for materials ore handling to the ROM. Current mining production activities have extended to a depth of 860m below surface. The typical mining method employed is modified avoca, although multiple mining methods such as uphole retreat, open stoping, flat backing and benching are also employed. Stope voids are backfilled either with unconsolidated waste from development activities or CRF - waste rock mixed with cement to create a cemented fill material that can be later exposed in the extraction of economic ore abutting the CRF material.
Processing
- Agitated tank (VAT) leaching
- Carbon in pulp (CIP)
- Elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Flow Sheet:
Summary:
Ore treatment/processing method/s: Free milling and treated by conventional crush-grind-CIP processing to produce gold-silver dorè.
Screening plant/equipment:Jaques Torrens double deck screen, top deck passing 24mm, bottom deck passing 10mm.
Mineral liberation/recovery method:Cyanide leach followed by CIP adsorption.
Mineral/fuel processing/recovery plant/ equipment:Denver 14m diameter pre-leach thickener, 3 Leach Tanks ea 3 3 540m , 6 Adsorption Tanks ea 155m.
Cyclone Feed pumps:Krebs Millmax 8" x 6".
Chemicals/reagents used:Sodium Cyanide, Hydrochloric acid, Sulphuric acid, Sodium Hydroxide - Orica; Hydrogen Peroxide - Solvay Interox; Hydrated Lime - Uni Min.
Recoveries & Grades:
Commodity | Parameter | 2019 | 2018 | 2017 | 2016 |
Gold
|
Recovery Rate, %
| ......  | ......  | ......  | ......  |
Gold
|
Head Grade, g/t
| 4.8 | 5.63 | 5.45 | 5.92 |
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Reserves at December 31, 2018:
Category | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
0.34 Mt
|
Gold
|
5.76 g/t
|
63 koz
|
Probable
|
0.81 Mt
|
Gold
|
4.77 g/t
|
124 koz
|
Proven & Probable
|
1.15 Mt
|
Gold
|
5.07 g/t
|
187 koz
|
Measured
|
0.27 Mt
|
Gold
|
9.04 g/t
|
79 koz
|
Indicated
|
1.09 Mt
|
Gold
|
6.47 g/t
|
227 koz
|
Inferred
|
1.59 Mt
|
Gold
|
2.88 g/t
|
147 koz
|
Total Resource
|
2.96 Mt
|
Gold
|
4.78 g/t
|
454 koz
|
Aerial view:
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