Production geology is responsible for the grade and tonnage that is mined from the ore lodes each day. They must also ensure that all of the lodes are trucked from the pit floor up to the Fimiston Plant.
To find the ore lodes the Mine Geologist must plan drilling and take samples of the rock beneath the pit floor. The method used to collect the samples is called RC drilling. The RC holes are drilled every 10 metres along the lode and 8 metres across, samples are collected every 2 metres down the drill hole. Because of the old underground workings most of the RC holes are drilled to 40 metres beneath the pit floor. The samples are then sent to the KCGM laboratory and are fire assayed for gold and sulphur.
When the gold and sulphur grades are sent from the laboratory, the geologist must plot the position of each of the drillholes onto a plan. From the plan, a map is produced of where the gold lodes occur beneath the pit floor. From the map, the tonnes and grade of the gold in the rock to be mined is determined. This map is used by the Drill and Blast Engineers, who drill all of the rock in the pit floor and fill it with explosives so the ground can be broken and dug by the face shovels. The map is also used by the Mining Engineers so they can mine and truck all of the ore lodes to the Mill and truck the waste rock to dumps that do not contain gold lodes.
The Mine Geologist must then work closely with the Drill and Blast Engineer to determine the best way to blast all of the rock in the pit floor. Each blast at the Super Pit has over 100,000 tonnes of rock that is broken. Each blast breaks the rock 10 metres below the pit floor.
After blasting the ore lodes in the broken ground are marked up with pegs and flagging tape so they can be easily identified by the mining face shovels. The surveyors survey in the boundary’s of the ore lodes by use of equipment that receive coordinates from satellites. Most of the ore lodes in the Super Pit have a pink - brown staining (alteration) around them. These can be seen by the human eye. To make sure all of the economic ore lodes have been identified, the blast rock is washed down by water. After washing, the geologist can then walk over the blasted ground and peg out the ore lodes by using the surveyors coordinates and by the colour of the ore lodes in the rock.
Once the ore lodes have been marked up on the pit floor the Mine Geologists work closely with the Mining Engineers so that all of the ore lodes are mined. It is the Mine Geologists job to determine the way the ore lodes are mined by the shovels. They often sit in the face shovels with the miners to ensure that only the ore lodes are mined, and that rock that does not contain any economic gold is trucked to a waste dump.
The Mine Geologist must also work with the Metallurgist to assist them in extracting the maximum amount of gold in the Mill Processing Plant. The geologist informs the Metallurgist of the grade of the gold in the ore lodes and the amount of sulphur that occurs in them.
After the gold bars have been poured the geologists compare their estimate of the gold that was mined from the pit with the gold that was recovered in the gold bars. This process is called reconciliation. The geologist does this study to help them identify if there are any problems in the way they identify and mine the gold from the pit floor.