The Diamond Mines of South Africa 353 



are brought up daily from a depth of 

 more than one thousand feet and spread 

 over the floors. These floors are made 

 by removing the bush and grass from 

 fairly level stretches of ground. After 

 clearing the face of the ground it is 

 hardened and smoothed with heavy rol- 

 lers until it is fit for use. 



After the blue ground has been spread 

 out, it is necessary to wait patiently until 

 the sun and rain have contributed their 

 service in disintegrating the breccia. The 

 effect of the exposure of this curious 

 compound to heat and moisture is very 

 remarkable. Large pieces of blue, which 

 are as hard as sandstone when freshly 

 taken from the mine, soon begin to crum- 

 ble on the depositing floors. To hasten 

 the disintegration, the bed of blue is har- 

 rowed several times to turn up the bigger 

 lumps and expose fresh faces of the 

 ground to the sun. Spans of mules were 

 originally used to drag the light harrows 

 used in those days, but steam traction 

 engines are now employed to draw 

 wheeled harrows with huge teeth back 

 and forth across the floors. So the great 

 spread of the floors looks like some vast 

 plowed farm where the laborers are pre- 

 paring the soil for seed. 



The diamonds are invisible. During 

 the fifteen years of my charge of the De 

 Beers mines I have never found a dia- 

 mond on the floors. 



Under normal conditions soft blue 

 ground becomes sufficiently pulverized in 

 from four to six months, but it is better to 

 expose it for a longer period, even for a 

 whole year. 



The ground is then carried in auto- 

 matic trucks to the washing machines, 

 where it is mixed with water to a very 

 thin mud and passed through a series of 

 pans and screens. Fifty per cent of De 

 Beers ground, when well pulverized, will 

 pass through a screen with holes one- 

 sixteenth of an inch square. 



When the day's work is completed, the 

 pans, through each of which three hun- 

 dred loads have passed, are emptied or 

 "cleaned up," and the concentrated de- 

 posits of diamonds, mingled with other 

 heavy but valueless minerals, are then 

 sent to the pulsator, which separates the 

 diamonds sufficiently for the sorting 

 tables. 



The work of picking out the diamonds 

 by hand from the concentrate on the sort- 

 ing tables was, of course, necessarily 

 slow and tedious. It was the only divis- 



Washin"" Machine 



