WINNING THE DIAMONDS	9
	the difficulty of any approach to complete watering may be readily imagined. 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.
	A certain percentage of the blue ground is not affected by exposure on the floors. This intractable ground, which is called hard blue, makes up about 5 per cent of the product of De Beers mine. The large pieces of hard blue are removed from the floors to be crushed in rock breakers and rolls, and large, worthless boulders and stones embedded in the blue, as well as large pieces of basalt and shale which fill the open mines, and