soil differed from a sample taken over a known pipe from a sample taken in an area where no pipe existed.

It was discovered that the termite soil sample - the geochemical sample - taken from a termite mound situated over a pipe contained different elements. A great deal of work was done refining this process and KDC is now totally confident it works.

During a 6-month period from November 1998 to April 1999, KDC's field staff collected 4,300 geochemical samples, which ultimately resulted in the discovery of 18 new lamproite pipes.

The full exploration process now follows a regimented pattern.

The geochem samples are collected from termite mounds in the field with a sample taken every 50 metres on 100-metre spaced grid lines.

The geochem sample is sieved and processed at the camp before being sent to Perth where each sample is carefully recorded and logged before being dispatched to laboratories for analysis.

The results from the laboratory are then collated and processed and KDC is able to determine a potential target area (an anomaly) from these results.

The anomaly is then drilled, usually to a depth of around 15-20 metres. A composite sample of the aircore drilling is collected at 3 metre intervals and sent for geochemical analysis. If the drill samples are anomalous, a further composite sample is collected.

The composite drill sample, weighing about 20 kilograms, is again sent to Perth for further laboratory analysis, but this time the laboratory is looking for diamonds, microdiamonds, garnets and chromites. If two or more of these indicators are found in the drill sample, hopes are high that a new pipe could exist.

The next step is to redrill the target area in an attempt to define the size and extent of the target and again these composite drill results are sent to Perth for detailed analysis and confirming the existence of a pipe. This is followed by excavating the pipe, taking up to 4 separate bulk samples of olivine lamproite and removing between 100 and 300 tons of material from the pipe.

The olivine lamproite is trucked to the ore pad next to the heavy media separation plant, located near the KDC camp.

The olivine lamproite is then processed through the HMS Plant where a concentrate of material having a specific gravity of greater than 2.9 is produced. A diamond has a specific gravity of 3.5.

The concentrate produced from the HMS Plant is divided into 4 separate size fractions, namely:

.7 millimetres to 1.2 millimetres
1.2 millimetres to 3.5 millimetres
3.5 millimetres to 7 millimetres and
7 millimetres to 10 millimetres.

This concentrate is then dried through the furnace drier before being put through a magnetic separator which removes any magnetic ironstone.

The final concentrate is then packaged in drums and trucked 2,700 kilometres to the Remote Systems Sortex Plant in Perth.

The Sortex Plant basically scans the gravel for diamonds. Diamonds emit visible light when bombarded by x-rays. The three largest size fractions of the HMS concentrate pass through the Sortex Plant, which picks out any fluorescing material (such as diamonds and quartz). If any material fluoresces, a jet of air blasts this material into a separate sealed box.

This box is removed and the contents are visually observed with all diamonds being removed. The tails from the Sortex are then run over a grease table as a way of determining whether the Sortex is working efficiently; any residual diamonds stick to the grease and are then removed. If the Sortex is working efficiently, no diamonds should appear on the grease table.

The diamond results are collated back to the tonnage removed from the pipe and a grade, expressed in carats per 100 tonnes, is calculated.

courtesy:kimberleydiamondco.com.au