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ANPET EXPLORATION PTY LTD
ACN 079 912 842 / ABN 13 079 912 842
PO BOX 625
PENNANT HILLS NSE 1715
AUSTRALIA
PH / FAX: +61 2 9875 5446
Email: [email protected]
MEMO
Date: August 13, 2001
Assessment of Super Sluice Recovery
On 13th of July Grahame Bush and I met Martin Marks at O'Allan Ford on the Shoalhaven River near Nerriga. The site is adjacent to a closed alluvial gold mine that I visited about 14 years ago. The purpose was to assess whether the equipment could live up to the claims made by Marks for recovery.
The Shoalhaven River is a large river at this site with a high gradient. There are numerous small goldfields upstream of this locality as well as in the immediate vicinity. Bed of the river at the ford is approximately 80 metres wide with the water restricted at this time of low flow to approximately 10 metres wide. The bedload consists of well rounded cobble to pebble sized material with about 60% sand. Bars vary from cobble dominated to sand dominated, with all variations in between. Individual bars have a length of over 150 metres.
Sites selected for testing were nominated by Marks. The first site was cobble dominated and was a logical choice for high gold concentration.
The second site was specifically selected by Marks after a request from me for a fine gold area. I believe that the site would have contained the finest fold present in the system at that locality.
The equipment tested was a very small back packable sluice with adjustable legs, a very small 2 stroke powered pump and layflat hose to deliver water to the sluice. The sluice was fed with a shovel. The sluice was constructed from fibreglass resin, contained built in rifles and was a refined version of sluices that are in widespread use for small production and recreational use. The equipment however consisted of an integrated and matched system that was easy to transport, set up and use.
Approximately 150kg of gravel with 25% sand was shoveled into the top hutch of the sluice where the spray bar washed the gravel and washed all but the largest stones (»100mm) down to the lower hutch where most gold is recovered. Some larger gold remained trapped in the upper hutch where most gold is recovered. Stones were removed by hand from time to time when the water flow was restricted by blockages. In my opinion the sluice could have been run more efficiently with closer sized feed insteadof ROM. This procedure was repeated on a second 150kg sample from the first site and then the equipment was moved to the fine gold area.
Tailings were systematically checked from the samples with no pannable gold detected in tailings of the first sample and only one colour of about 0.5mm detected from the second sample. This compared with recovery of several hundred colours from sample 2 from the first site. Gold size was all less then 1000 microns, with the smallest size seen being about 40-50 mocron. Recovery was clearly well in excess of 95%, a remarkably high figure for a sluice. Grade of the gravels at the first site was estimated at approximately 1.3g/Au/m3.
A sample of about 200kg was tested from the fine gold site, that had about 50-60% sand and pebbles to about 50-75mm size. Some problems with excessive water flow were corrected by reducing pump engine speed and sample shovelled in as fast as it could be dug up. Tailings were sampled twice, with the tailings directed into a pan for up to a third of the sample treatment time. the recovered tailings were panned off and about 15 medium and fine colours were recovered. These were flattened and ranged up to about 15 medium and fine colours were recovered. These were flttened and ranged up to about 30 micron in size. Concentrates contained an estimated minimum of 500 colours, with sizes ranging from about 40-50 microns up to 1000 microns (1mm), with the majority of gold being about 100 micron, considerably smaller than the average size at the first site. The lack of finer gold is probably a fiuncti8on of the river system rahter than the capabilities of the sluice as no finer gold could be recoverred in careful panning of material from the second site. Minimum size of gold recovered from 10kg of sample was about 50 micron with a total of approximately 80 colours recovered, ranging up to about 500 micron in size. Recovery is estimated to be in excess of 95% on the second site sample.
Wash up of the sluice was very quickj and simple, achieved by washing down the riffles with a small watering can into a pan. In production semi continuous concentrate recovery, without plant shut down, would be by venturi dumping into a holding tank prior to processing further to recover a higher grade concentrate.
Gold shape tended to be flattened but rough, possibly due to secondary overgrowths of gold on many of the grains. The gold is not as grainy as that at Lalat and consequently better recovery can be expected at Lalat with the same rate of feeding of the sluice.
Recovery by scaled up sluices may not be as good but is expected to still be much higher than traditional design sluices. The robust construction should lead to a relatively long life, even in a production enironment.
The purpose of the assessment was achieved with results surpassing the most optimistic expectations.
Peter Temby
MAIG, MSEG
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