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Last updated:  June 2006

The Mining Plant

Truckloads of wash are then carted to the plant. The mine plant consists of 3 main parts: a) the nozzle box, b) trommel and c) pulsating jigs. These 3 components can be seen clearly in the photo below - a test plant used for small scale mining and exploration.

Nozzle box: This consists of a large steel bin big enough to hold at least one truck load of wash – about 10 m3 in our case.  At the front of this bin is a large water nozzle, usually in a shed - here a workman spends his day washing the dirt and feeding the plant. This sometimes requires breaking up lumps of mud with a shovel and getting wet with spray - not a pleasant job during cold Glen Innes winters.

Trommel: Consisting of a large rotating barrel with paddle structures inside to help break up the wash as it passes through. This short video clip shows the trommel working. This also has a series of different size screens sizing the material with large going straight through and small being channelled to the next important part of the plant: the pulsators.

Pulsating jigs: These jigs pulsate (us miners are inventive with names) using the simple principle of water pulsing up and down over a stainless steel mesh base (see the video collection to show this).  The jigs are divided into individual sections which trap the heavier material (sapphire and black spinel are heavier than most other gravel) - the lighter material moves across the jigs while the heavier material settles in the divided sections. The best sapphire is always in the first couple of bays as it is heavier.

These bays are emptied or “robbed” at the end of each day. This concentrate is kept for further processing. We also carefully look through each bay as we rob the jigs, manually removing any larger stone. This is the best part of the day but can sometimes bring disappointment.

Any solid material which passes through the plant is taken back to the cut.  Water is recycled through the plant and slurry (liquid mud) is trapped in a series of settling trenches.  These must be regularly pumped out.

This is a hard game with huge running costs and often poor returns.  People who say “you’re lucky to be a miner” are often threatened with a hypothetical visit to the bottom of the cut. However, on good days the satisfaction of finding the best sapphire in Australia keeps you going.

The next stage involves processing the concentrate material retrieved from the plant - click here to go to the next page to learn more about this.