Already well renowned for gold as well as gravity recovery of base metals, APT has designed and launched a series of plant designs for gem stone recovery.
“Gemstones have various properties that enable separation and recovery, some have a higher SG than the gangue, like diamonds and rubies and can be separated by gravity techniques. Some fluoresce and can be sorted under UV light, like diamonds, and in some cases it is down to simple eye recognition with hand sorting, like amethyst,” said CEO and chief technical adviser Kevin Peacocke. Whatever the recovery system dictated, the first requirement is to thoroughly disintegrate the host to liberate the gem and in the process remove the fine silt and clay. The physical properties of the gems in the resulting gravel can then be utilized to the full extent to make the separation.
This first stage is typically achieved in one of APT’s renowned RG scrubbers which are legendary in breaking up tough clays as well as loose agglomerates. The deep drum design of the scrubber means that autogenous attritioning takes place and the tumbling action thoroughly cleans the surface of the gems without mechanically breaking them. Drum speed can be varied to obtain the most optimal action for each case.
The resulting slurry is then screened on the in-built trammel to recover the gem containing gravels to the oversize whilst discarding the fines. Spray jets complete the cleaning process and the gravels are ready for the next step. If the gem has a high SG, this will typically utilize a jig, and sometimes an extra jig is added to treat the coarse oversize as there may just be a few large bonus stones to be recovered.
In its simplest form the screened gravels are directed to a picking belt where practiced eyes scalp off the coloured gems, as is the case with amethyst or other silica crystal species.
Figure 1 APT RG200 scrubber suitable for 20tph operation
Piloting and small scale production
Being APT, the smaller scale has not been neglected. A small scrubbing , screening and jigging plant is available for the 1-3tph scale which greatly enhances the capability of the artisanal sector. “The same unit can of course be used as a pilot plant for large operations, or as an exploration tool”, said Peacocke, who explains that a similar unit has recently been commissioned in Mozambique for this purpose.
Figure 2 APT RG30 pilot plant for 1-3tph, with jig separation
APT can test your samples through their associate laboratory Peacocke & Simpson, fully equipped to handle large bulk samples of up to one tonne.
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