Kimberley Diamonds: Especially Cleavage Diamo7ids. 
91 
diamonds can grow if they get suitable opportunities ; tliey got plenty of 
opportunities in Wesselton and Bultfontein, but not many in Dutoitspan. 
Thus, on this view, there is a relativity between 
(a) The numerous accretionary structures ; 
(3) The frequent foreign inclusions ; 
(y) The numerous and small diamonds, of such a mine as Wesselton, 
and ; 
(a') The few accretionary structures ; 
(/3') The rare foreign inclusions ; 
(y) The fewer and larger diamonds, of such a mine as Dutoitspan. 
And this view is confirmed to my mind by such casual inspection as I have 
been able to make of diamonds won from mines situated outside the 
Kimberley district. In particular we may say that where diamonds are 
few or many in number, in any mine, there accretionary structures will 
be rare or numerous respectively. Wesselton diamonds are singularly 
accretionary. 
How far apart from one another Kimberley diamonds in situ are may be 
illustrated by some examples. From May 16th to June 5th, 1917, eighteen 
working days, 129,640 loads, 2,074,240 cubic feet, of Dutoitspan blue ground 
were washed, yielding 20,957 carats of diamonds of all sizes, of which a first 
count gave 40,800 tiny diamonds averaging 78 to the carat (and only worth 
a penny a piece !), and 36,600 larger ones, of which one was of 126 carats and 
another of 174 carats ; 77,400 diamonds in all, or one to every 27 cubic feet 
of broken blue ground, equivalent to one diamond to every 17 cubic feet of 
solid ground before mining. A similar count for Bultfontein showed 
174,300 tiny diamonds and 207,900 larger ones, 382,200 in all, in 940,390 
cubic feet of solid ground, or 1,504,624 cubic feet of broken ground, i. e. one 
diamond to every 2^ cubic feet solid, or to every 4 cubic feet loose. Corre- 
sponding Wesselton results are 210,000 tiny diamonds, and 232,000 larger 
ones, 442,000 in all, in 1,717,730 cubic feet of solid ground, or 2,748,368 
cubic feet of broken ground, i. e. one diamond to every 4 feet solid or to 
every 6i feet loose. 
Before passing to other matters, it is worth while to suggest that the 
prevalent rounded form of yellow diamonds is not due, as has been sug- 
gested, to attrition or abrasion — the sulcate surfaces of these is suggestive 
of anything but that — but to the temperature at which they were crystallised 
and the influence of the colouring matter they contain.* Some such reason 
may account for the Pool or the Dutoitspan macles. A remote analogue is 
the fact that it is the presence or absence of magnesia which has determined 
* " Rounded edges and other surface irregularities may, however, result from the 
corrosion of a crystal subsequent to its growth " (L. J. Spencer, Art. " Crystallo- 
graphy " in ' Ency. Brit./ 11th ed., 1910). Surface abrasion is only shown to perfection 
on diamonds won from alluvial gravels. 
