MMG Rosebery 14 July 2015 History of Rosebery
1893 • Tom McDonald discovered alluvial gold with boulders of zinc-lead sulphide.
1920 • Rosebery and Hercules Mines purchased by the Electrolytic Zinc Company of Australasia Limited. (EZ).
1927 • Construction of Rosebery Mill begins.
1936 • Production started in February – Mill capacity was 15 tonnes/hour.
1961 • Mill capacity was 30 tonnes/hour.
1963 • Murchison Highway completed.
2003 • Breakthrough of surface decline allowing trucking of ore to surface.
2004 • Transition from Pasminco to Zinifex Ltd., becoming one of Australia’s leading companies in mining and producing zinc, lead, copper, gold & silver.
2008 • Zinifex Ltd and Oxiana merged into OZ Minerals.
2009 • MMG – Minerals & Metals Group.
2011 • 75 years of continuous mining and milling at Rosebery.
2 Overview
Location: Tasmania, Australia Ownership: 100% MMG
Mine: Underground (sublevel open stope – Transverse, Longitudinal and slashing stoping)
Throughput: 0.95 Mtpa, mine, crush, grind, float
Product: Zinc concentrate, Lead concentrate, Copper 2014 Revenue by commodity concentrate, Dore gold/silver. 3% 16% 12% Mine Life 2023
17%
52%
Copper Gold Silver Zinc Lead 3 Site Layout – Proximity to township
3 1. Portal.
2. Concentrator. 6
3. Filter Plant & Train Loading 2 1 Station. 5 4 4. Administration Building.
5. Old 3 Level Open cut. 7
6. Waste Rock Dump.
7. Rosebery1 Hospital.
Geology – Volcanogenic Massive Sulphide (VMS) deposit
Characteristics of VMS Deposits Trilobite
Size <1Mt to 50Mt to giant deposits (500Mt) e.g. Kidd Creek, Brunswick 12, Neves Corvo
Polymetallic, Rosebery -Zn, Pb, Cu, Host Au, Ag
Stacked Deposits, Repetition through rock sequence
Occur as clusters within belts (3 to 6 km separation) Mt Read Volcanics of Tasmania, Iberian Pyrite Belt, Green Tuff Belt of Japan
Present day analogue of VMS deposits are Black Smokers
5 Geology – Volcanogenic Massive Sulphide (VMS) deposit
Size - >50Mt of massive to disseminated sulphide.
Mineralogy - Sphalerite, Galena, Pyrite, Chalcopyrite, Electrum (Au containing Ag).
Orientation – Orebodies strike NNE and dip at 43° to east.
Host Package – Sequence of felsic volcaniclastics.
Structure – Strong cleavage between two large reverse faults, Mt Black and Rosebery faults. Rosebery Y lens Orebody
Mine Overview – Surface Underground Interaction
6 5
> One of the longest and deepest mines in operation currently in Australia (1,500 metres).
> Mining areas (K, N&P, W, Y&X).
> Mining – Ore: Zinc (Zn), Lead (Pb), Copper (Cu), Gold (Au) & Silver (Ag). Mine Overview - Current Production Areas Metallurgy flow sheet
9 Crushing and Grinding
> The Rosebery crushing circuit consists of a Primary Jaw Crusher and a Secondary Cone Crusher.
> During Crushing the ore size is reduced from around 650mm to P80 of 20mm.
> The Grinding Circuit consists of 2 x Primary Ball Mills and 3 x Secondary Ball Mills.
Secondary crusher Primary ball mill 10 Gravity Gold
> Gravity gold is recovered from the grinding circuits using 2x Knelson Concentrators.
> Gold Concentrates are leached in an Intensive Leach Reactor (ILR).
> Then recovered from the pregnant leach solution by electrowinning and thereafter the gold sludge is smelted.
11 Gold pour Gold Doré bar Flotation
> The recovery sequence for sulphide minerals in the Flotation Circuit is Chalcopyrite (Cu) → Galena (Pb) → Sphalerite (Zn).
> Payable gold and silver is recovered with the copper and lead concentrates.
Copper float cells Lead float bubbles
12 Filtration
> Concentrates are pumped to the Filter plant where they are filtered using Larox Filters.
> The filters produce a dry concentrate that is then transported via rail to Burnie.
Lead Larox filter Zinc concentrate
13 Concentrate Shipment
> From Burnie, concentrates are shipped to final destination by sea.
Zinc concentrate being offloaded at Nrystar in Risdon Tailings – Dams
> Tailings is disposed of in the Bobadil Tailings Storage Facility (TSF) that is situated approximately 4km from the processing plant.
> The tailings slurry is pumped into an open flume that transports the material to the Tailings Storage Facility. Marketing
Products: Zinc concentrate Lead concentrate Copper concentrate Gold Doré
Production: 2015 guidance (metal in concentrate) Zinc: 80 - 85 kt contained zinc Lead: 22 - 24 kt contained copper
Product sales: • Life of Mine/Life of Smelter contract with Nyrstar for 100% of produced concentrate. • Concentrate is transported by rail to Burnie Port. • Rosebery Zn and Pb is sold on FOB basis at the Burnie Port. • Zinc is transported to Hobart, Lead to Port Pirie, Copper on the open market and Gold Doré to Perth Mint. • MMG have exported some quantities of zinc concentrate in the past when Nyrstar
16 offtake fell below production. Marketing
Zinc Concentrate > Relatively high Zn grade (+54%), with relatively low Fe and acceptable impurity content.
> Precious metals content close to payability thresholds.
> Attractive Zn concentrate in China / Asian markets.
Lead Concentrate > Relatively high Pb and Ag grade, along with high Zn grades and low impurity levels.
> Attractive contract with payments for contained Zn, Pb, Au & Ag.
Copper concentrate > A complex concentrate with high precious metals and high impurities - limits buyers.
> Currently selling under a Frame contract to a trader for blending with cleaner materials. This enables the value of high precious metals and copper to be realised.
Dore’ concentrate > Transported to Perth Mint for refining, containing approximately 60% gold and 30% silver. 17
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