90 Transactions of the Royal Society of South Africa. 
Pool. Dutoitspan. 
Per cent. Per cent. 
Stones other than brown or yellow . 11-56 . 13-29 
Cleavages other than brown or yellow . 22-15 . 23-90 
That is, the ratio of yellow cleavages to yellow stones is less than the 
corresponding ratios of brown or of colourless diamonds. It must have 
been on the basis of some such results as these that Bauer thought he had 
discovered that coloured diamonds resist fracture better than white ones. 
Pool information was probably all he had at his disposal at the time. 
The significance of the above Pool and Dutoitspan statistics is to be 
gathered from the fact that foreign crystal inclusions in yellow diamonds are 
scarce. It is rare indeed for a yellow diamond to conje in with a garnet or 
other mineral embedded in a broken face ; and still more for such a mineral 
to be seen inside a whole stone. With regard to the latter contingency, 
however, it must be admitted that it would not always be easy to see an 
inclusion through the common sulcate faces of a yellow stone, though the 
former is evidence enough that foreign inclusions cannot be frequent. 
Again, South West African diamonds are often yellow, and the percentage 
of cleavages to stones is not great among them. An irregular yellow 
diamond, with grey corners, in my possession contains a garnet in a broken 
face. A piece of the garnet has been broken away exposing an excellent 
surface of attachment on the diamond. Spaces in the cavity between the 
diamond and the garnet are filled up here and there, as usual, with an opaque 
white substance. 
The impression one gathers by way of inference from all these particulars, 
as well as from a scrutiny of the produce of the various mines round about 
Kimberley, is that nearly every yellow stone was formed rapidly in one piece 
out of a single bubble of liquid carbon (stained with iron oxide), or out of 
a bubble of some solvent containing carbon, thus occluding foreign solids ; 
whereas the Wesselton or the Bultfontein octahedron was built up more 
slowly, step by step, and layer by layer, thus incorporating foreign solids 
in the diamond mass. Naturally, a small, loose, foreign, solid body in a 
cavity larger than itself, occupied by a carbon bubble, would lie at the 
bottom of the hole if its specific gravity were greater than that of the 
bubble, or at the top if its specific gravity were less, and in either case need 
not be imprisoned in the final diamond crystal, though it might stick to a 
natural face of it. In the case of a diamond crystal continuing to grow by 
accretion of matter from adjacent carbon bubbles, the foreign solid might be 
imprisoned in the crystal, but not otherwise. Now clearly there would be 
more chance of this accretion in magmas where the bubbles were smaller 
and more numerous — as must have been the case for certain in the Wessel- 
ton and Bultfontein Mines, — than in magmas where the bubbles were larger 
and much further apart, as at Dutoitspan. In other words, assuming that 
