Burnstone lies within the Witwatersrand Basin and Archaean (2.7 billion year-old) sedimentary basin. The Basin is filled with approximately 14,000m sedimentary and subordinate volcanic rocks, which have been folded along a north east to south-west axis into an asymmetrical synclinorium. The sediments consist mainly of quartzites and shales and less prevalent, but generally economically important, gold-bearing conglomeratic zones, which occur on regional unconformities. These are commonly referred to as reefs or placers.

Burnstone is located in the South Rand Basin, a subsidiary of the main Witwatersrand Basin. The gold-bearing target UK9 Reef of the Kimberley Formation, occurs in the Central Rand Group of rocks. This reef lies between the outcrop and a depth of 1,300m below surface in the mining right area. Structurally, the project area is located on the northern limb of the arcuate South Rand Basin, which is locally deformed by a east-north-east-plunging anticline and cut by east-west and north-south normal faults, formed in response to the stress regime corresponding to the main structural feature of the region, which is the east-west striking Sugarbush Fault. This fault is a left-lateral wrench fault, which comprises the northern boundary of the South Rand Basin at this point.

Shallow gold deposit exploiting the UK9a Reef of the Kimberley Formation, Central Rand Group, Witwatersrand Supergroup.

The UK9a Reef is a thin (<1m), highly channelised, shallow dipping (<10º) orebody. The minimum mining cut includes waste to a total of 110cm.

The Burnstone project has two established access points into the underground workings: a three-legged decline shaft and vertical shaft.

The mine is accessible via an existing decline shaft and an equipped vertical shaft. To access the down-dip extents of the orebody a number of declines have been planned and development is progressing. Underground infrastructure includes the shaft, silos, conveyors, chutes and rock breakers on the main rock handling levels at the shaft, loading boxes in the shaft, workshops, clarification and pumping systems, water dams and electrical reticulation and communication systems. Excavations include pump stations, settlers, declines, horizontal drives and stoping infrastructure. There is a limited fleet of underground trackless mining machines (TMM) including one roof bolter, one dump truck, one development rig, one long hole rig, two LHDs, two graders, utility vehicles, Manitou forklifts, and LDVs. Production and development drilling are by hydropower and power packs.

All surface infrastructure to support the underground mining is in place or has been planned in the LoM with an appropriate capital estimate. The current trackless fleet, which will be used to develop, has been scheduled for replacement or refurbishment in the LoM capital estimate. A mineral processing plant is situated next to the vertical shaft where the bulk of the tonnage will be hoisted. It is currently on care-and-maintenance and will be started after a year of mining when a suitable stockpile has been established. A TSF has also been established a short distance from the processing facility. Other surface infrastructure at Burnstone includes the headgear and winders, primary ventilation fans, compressors, the processing plant, office blocks, training centre, workshops and stores, lamp room, change house, stores and store yards. There are also established roads, a sewage treatment plant, potable water plant and surface water reticulation. Electrical infrastructure consists of a main incoming substation and surface reticulation. The mine is using the Pragma CMM System for maintenance management.

Mining method: Hybrid of conventional selective scattered breast mining with scraper cleaning, together with mechanised footwall infrastructure.

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After the ore is extracted underground, the plant will treat 125 000 tonnes per month of ore
and will consist of the following process steps (Knight Piésold, 2007):
• Jaw crushing;
• SAG/Ball milling of underground ore to 80 % -75 µm;
• Dense cyclone overflow (40 % solids);
• Gravity separation of cyclone underflow material;
• Cyanidation in six tank carbon-in-leach circuit;
• Gold adsorption onto activated carbon and stripping via Zadra elution;
• Carbon regeneration in horizontal electric kiln;
• Gold electrowinning and smelting;
• Tailings thickening; and
• Tailings disposal to conventional TSF.

Gravity Circuit
The bleed stream, diverted to gravity concentration from the mill cyclone cluster underflow, will be passed over a vibrating scalping screen to remove coarse (+3mm) particles, which will gravitate back to the mill inlet chute. Spray water will be applied to the screen deck to improve screening. Screen unde ........