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Transactions of the Royal Society of South Africa. 
African diamonds is so eminent tliat even the heat of the hand causes some 
of them to fall to pieces. Such diamonds, generally octahedra, may be 
recognised by a peculiar watery lustre : they are called plate diamonds." 
2. Observations and Experiments. 
Some of my own observations and experiments bearing on the question 
of broken diamonds may be of interest : 
(1) A broken Koffyfontein diamond of good whiteness, of about four 
carats, and one-half the size of the original whole stone. There was a hole 
in the middle of the fractured face containing small pieces of foreign minerals, 
chiefly black. Held in a strong light under magnification a tiny crack, 
transverse to the fractured face, could be made out in the vicinity of the 
hole. A sharp jerk between thumb and finger broke the specimen through 
the crack as easily as a match can be broken. Some apopbyllite had pene- 
trated the crack. It is a fair inference that the original diamond crystal- 
lised, and broke, about some mineral inclusion. The half examined was in 
so precarious a state that merely dropping it on the table might have broken 
it. Anyone overlooking such a crack, as they easily might, and putting 
such a diamond away, say by tossing it in its paper envelope or pillbox into 
a safe, would find it broken the next day. And the incident would be 
quoted as another proof of the bursting of diamonds. KofEyfontein 
diamonds, it may be added, show more tendency to crack in two directions 
at right angles than do the diamonds from the Kimberley area — perhaps 
because of their prevailing irregular shape. 
(2) Mr. Scott Ronaldson was good enough to show me a dull brown 
Kimberley Mine octahedron recovered from old debris which was seen to be 
slightly cracked when he bought it. Later it split in twain, showing then 
that it had crystallised about a smaller octahedron of somewhat similar 
colour and appearance, though of different orientation. Here again there is 
no need to invoke bursting. The case is just the same as those mentioned 
in my previous paper, namely, the unequal expansion and contraction of 
enclosure and inclusion. 
In the De Beers collection there is a specimen resulting from the same 
process, half a diamond with an octahedron projecting from its broken face. 
The corresponding detached half has not been found. The projecting octa- 
hedron is remarkable in having rough edges like a Yaal River diamond. 
In my own collection is a beautiful little colourless specimen in which a 
cup -like shell of diamond (one-half its original size) holds fast an octahedron. 
There is no indication of what filled the space between the inner and the 
outer diamond. There is a better specimen in the De Beers collection, a 
white octahedron penetrating the face of another, the second being attached 
to a cup-shaped shell like the previous one. Between the cup and the inclusion 
is a yellowish foreign matter containing black grains. Portions of diamond 
