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Transactions of the Royal Society of South Africa. 
who lias had practical experience in finding these fragments that they were 
not crystallised where they are found." On the substructure of this evidence 
Wagner (p. 164) and Bauer (p. 195) assign the origin of Kimberley dia- 
monds to a deep-seated plutonic rock, claiming that the broken fragments 
owe their condition to violent eruptive outbursts which shattered country 
rock and blue ground alike.* The latter, however, stultifies his argument 
to a certain extent in his very next paragraph, where he states that the 
minerals and rock fragments in the blue ground show no signs of wear 
and tear. It is hard to see how the diamonds could have suffered so much 
damage and their kimberlite surroundings none at all. As a matter of fact, 
better authorities tell us that the rock fragments in the pipes do show a 
great deal of wear and tear. (See A. L. du Toit, " Geological Survey of the 
Eastern Portion of Grriqualand West," in the Eleventh Annual Report of 
the Cape Geological Commission, 1906.) Du Toit, it may be noted, pro- 
visionally accepts the theory that the shattering of the kimberlite accounts 
for the fracturing of diamonds, but observed that garnets have not suffered 
to the same extent (p. 151). 
11. Spontaneous Breaking. 
A more attractive theory, and one repeatedly quoted from one to the 
other by writers on the diamond, is that certain classes of diamonds fre- 
quently tend to break of themselves. G. F. Williams (p. 500) is responsible 
for the opinion that " light brown, smoky diamonds often crack on exposure 
to the dry air, but they will remain intact if kept in a moist place. The 
cracking is, therefore, more probably the result of heat or drying than of 
tension or inward [? interior] pressure. It is possible, however, that the 
great heat to which the diamond is exposed when brought to the surface 
may expand contained gases sufficiently to crack the stone." Crookes, on 
the other hand (Kimberley Lecture), seems to attribute the fractures to 
sudden lowering of pressure in the space surrounding the diamonds, and 
speaks of consequent explosions. G. H. Smith (p. 131), following Crookes, 
says that " so great is the strain that many a fine diamond has burst to 
fragments on being removed from the ground in which it has lain." 
Unfortunately, the evidence for this particular theory, as a complete 
theory, is not strong nor very extensive. What, at first sight, might look 
like a consensus of scientific opinion is, in reality, gossip handed on from 
one to the other by nearly all, and is by no means the outcome of indepen- 
dent research. Personally, I have met plenty of people who have heard 
of the bursting of smoky diamonds without ever having witnessed such a 
disaster with their own eyes, and the story of the custom of sending them 
to England inside potatoes is almost a chestnut. Certainly the De Beers 
Company never pack any of their millions of diamonds in potatoes. A 
* Cf. also L. J. Spencer in 'The World's Minerals,' p. 46, 1911. 
