Granny Smith

Granny Smith Mine - Mining Global Magazine

Granny Smith gold mine (GSM) is an underground gold mining operation located 740km northeast of Perth, Western Australia. Access to the site is via private charter flights or 950km by road from Perth.

Mining administration and maintenance is located at the Wallaby mine. Ore is processed at the Granny Smith CIP processing plant under campaign milling conditions and is located 12km east of the Wallaby underground mine.

Brief History

The Goanna and Granny Smith deposits were discovered in 1979 by CSR Ltd. In 1988 Placer Pacific acquired CSR’s 60% interest with the remaining 40% held by Delta Gold NL.

In 1989, mining at the GSGM commenced in the Granny Smith pit, and continued in subsequent years with the development of the Goanna pit, the Windich pit and nearby satellite pits. First gold was poured in 1990.

The Wallaby deposit was discovered in 1998, 12km west of Granny Smith, with first open pit ore delivered to the mill in November 2001. The Wallaby open-pit was mined from October 2001 until December 2006 and produced 1.5 million ounces of gold. Underground mining at Wallaby commenced in December 2005 and is ongoing. At the end of 2015 a total of 1.95 million ounces of gold has been mined.

Gold Fields acquired 100% of the Granny Smith Gold Mine on 1 October 2013 as part of the purchase of the Yilgarn South operations. and had an initial mine life expectancy of nine years. However, it has remained in continual operation since commissioning and at the end of 2015 has produced a total of 7.3 million ounces of gold.


Mining Operations

The current operations consist of the Wallaby underground mine with mining occurring in four ore lenses – Zone 70, Zone 80, Zone 90 and Zone 100.

Access to the Wallaby underground mine is via a portal established within the completed Wallaby open-pit. The mine operation is trackless, with truck haulage from underground via the pit ramp to the surface.

Two primary underground mining methods are used, with minor adjustments to suit localised geometry; Inclined Room and Pillar (IRP) is used in areas with a moderate dip (10° to 35°) and moderate width zones (four to six metres), and Transverse Long-hole Stoping (TLHS) is used in zones, which are thicker (six metres to 15m) with variable dips. Two other mining methods are used to a lesser extent: Narrow Vein Long-hole Stoping may be utilised in some areas with the benefit of reduced planned footwall dilution, and Bulk Long-hole Stoping is used in thicker zones (15m plus) under varying dip conditions.

The annual production of the Wallaby mine is in excess of 250,000 ounces per year.


Processing Plant

The Granny Smith process plant has a capacity of 3.0 million tonnes per annum. The plant was originally commissioned in 1990 to treat oxide gold ores mined from the Goanna, Granny Smith, and Windich pits. The plant has been periodically upgraded, with the last expansion completed in 2001/2002 to facilitate processing of the sulphide ore mined from the Wallaby underground deposit.

The plant consists of a two stage crushing circuit, a standard SAG and Ball mill (SABC) grinding circuit, a gravity circuit, a Leach/Carbon in Pulp (CIP) train, a pressure Zadra elution circuit, a tailings recovery (TR) circuit and a thickened tailings storage facility (TSF). Currently, the overall metallurgical recovery averages around 92.6%.

Camp Life

Fully contained ensuite rooms and well-equipped recreational facilities available to all residents are located on site. This includes a swimming pool, fully equipped gym, two squash courts, two multi-use sports courts (tennis, basketball, indoor soccer/cricket), and pool and table tennis tables. There is also a Wet Mess located adjacent to the dining facilities in the camp, with an ATM and communal television room available for all residents.

The site is exclusively fly-in fly-out and from Perth and the flight takes approximately 1 hour. Most roles operate on an 8 days on 6 days off roster. There are other rosters in operation including 4 days on 3 days off, 8 days on 6 days off 7 nights on 7 days off, with the latter typically reserved for production employees.