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Transactions of the Boyal Society of South Africa. 
again in the mines of Griqualand West. More important still, incrusted 
stones have been proved to exist inside larger ones. A good and typical 
instance was a Dutoitspan fragment of about two carats consisting of about 
a third of a whole white rounded diamond. Portions had split away from 
the original whole stone along two octahedral planes of cleavage, showing 
near the middle of the edge where the cleavage planes met a heavily 
incrusted little stone of fair form, as depicted on an enlarged scale in the 
annexed Fig. 1. The incrustation was at least as hard as ordinary 
diamond. Observed through what was left of the natural face the inside 
of the fragment appeared to be extensively blurred with large black blotches 
A 
D 
Fig. 1. — Section of fragment showing position of inchision. a. Incrusted 
inclusion, ab. Cleavage faces, bdb. Natural surface. 
— an illusionary effect caused by refraction, for actually, saving for the 
incrusted inclusion, the specimen was quite without blemish. Soft graphite 
inclusions are plentiful enough in the holes so common in the cleavage 
surface of diamond. 
Owing to the high refractive index and frequent rounded habit of 
diamond the true outlines of black spot inclusions are not always easy to 
make out, but frequently they seem to be shapeless. Sometimes they are 
mere flakes. They occur either singly or in groups. Jagersfontein diamonds 
are noted for the dense and solid appearance of their large black spots. 
At the other end of the scale of size are the smoky-brown clouds — the 
danger-signals of sensational literature, giving warning of impending 
