TREATMENT OF ORE

The recovered ore must be processed in order to obtain the diamonds. It is first crushed with crushers, set l|-inch apart. It is reckoned that this method is good enough to pass most diamond ring without damage possibilities. The reduced ore is then passed by conveyor belt to a washing plant capable of dealing with 1000 tons of blue ground per hour. The ore is I he re mixed with a puddle of muddy water and then transferred to an annular rotating pan 14 feet across, where it is mixed by rakes.
Now, diamond is heavy (density 3-5 times that of water), whilst the density of the puddle liquid is only 1-3, so the diamond easily sinks to the bottom of the pan from which it is raked out by helical raker arms. The lighter mass is then re-processed with f-inch crushers to catch the smaller diamonds, and this again later re-crushed to trap still smaller sizes.
This crushed material is in each case sent to a second pan and is further treated. The concentrates obtained from these treatment pans are now ready for the more refined process needed for final recovery. Between the years 1907 and 1952 I he diamonds were extracted with a machine called the ‘pulsator’, but this has now been replaced by a new method of treatment which is more effective and cheaper to operate.

In the newer method the output from the pans is first screened for small-size material (fines) by being passed over small-mesh stainless steel screens which are vibrated. The lines which pass through the screen are treated with a grease table in the manner to be briefly described later. The main concentrates then pass on to what is called the 'heavy media separation cone'. This is essentially a conical flotation vessel which has in it a high-density liquid, a puddle of ground metal powder of ferro-silicon which as a puddle ,has the high density of 3-0.
The diamonds sink in this vessel, and as it is conically shaped they concentrate at the lower tip. In due course this concentrate meets a vibrating grease table, for complete extraction.