Kimherley Diamonds : Esi^ecially Cleavage Diamonds. 
93 
For the 12 months 
Wesselton. 
Bultfontein 
ending" June 30th. 
(Carats.) 
(Carats.) 
1907 
32 
32 
1908 
27 
32 
1909 
34 
38 
1910 
32 
37 
1911 
27 
38 
1912 
29 
41 
1913 
27 
42 
1914 
28 
38 
1915 
26 
35 
1916 
26 
40 
If the diamond content of the pipes be assumed constant at all depths, 
we should expect that better methods of extraction with progress of time, 
to g-ive better yields. Since there are no signs of a better yield at Wesselton, 
the conclusion ought to be that the ground tliere gets slightly poorer with 
depth. At Bultfontein there would seem to have been an improvement 
with depth. At the latter mine there is a rough sort of correlation, acci- 
dental or not, between the yield and the quality of the diamonds given by 
it which may be expressed thus: When the yield of carats per hundred 
loads increases, the percentage of inferior diamonds tends to decrease ; in 
other words, the diamonds are of the best quality where they are packed 
closest together. When Nature had an abundance of material she used it 
well in the interests of the market ! This is for any given mine ; it does 
not apply comparing one mine with another. For instance, Bultfontein has 
a higher yield than Dutoitspan, but not such good diamonds. Bultfontein 
blue ground is somewhat patchy ; Wesselton, though poorer, is more 
uniform. 
The De Beers and Kimberley yields are published together as one 
Annual values are given in the following table : 
Tahle showing the Yield of Fool Diamonds. 
For the 12 months 
ending June 30th. Carats. 
1892 ... 92 
1893 . . . 105 
1894 ... 89 
1895 . . . 85 
1896 ... 91 
1897 . . . 92 
1898 . . .80 
1899 ... 71 
1900 ... 67 
1901 . . . 76 
