72 Transactions of the Royal Society of South Africa. 
of size. Taking all diamonds of 10 carats each, or greater, we have the 
following comparison: 
Year. 
Mine. 
Total 
production 
in thousands 
of carats. 
Averag-e siie of 
diamonds of, or 
exceeding, 10 
carats. 
Ratio of total 
weight of 
diamonds 
exceeding 10 
carats to total 
production. 
Number of 
diamonds of, or 
exceeding, 10 
carats each in 
every 100,000 
carats produced. 
Carats. 
Per cent. 
1898 
De Beers . 
1897 
18-2 
12-25 
674 
1898 
Kimberley . 
652 
17-0 
1165 
684 
191Z 
Wesselton . 
560 
15-5 
2-32 
140 
1912 
Bultfontein 
893 
14-9 
97 
65 
1912 
Dutoitspan 
o04 
200 
17-02 
850 
Thus diamonds exceeding 10 carats each in weight are relatively infrequent 
at Bultfontein, and average small ; whereas upwards of one-sixth of the 
Dutoitspan yield consisis of stones averaging 20 carats each. 
This is remarkable, seeing that these two mines are so close together that 
they could even be worked (though perhaps not very profitably) from the 
same inain shaft, and possibly have, as we have just said, some underground 
connection. Comparing one mine with another, the rule is essentially : The 
greater the average size of diamonds exceeding 10 carats each, the greater 
the ratio of their total weight to the total production, and the greater their 
number in every 100,000 carats produced. Kimberley Mine deviates slightly 
from the rule in the second particular. 
3. Less Obvious Differences. 
Besides all this there are the subtle differences, previously alluded to, 
between thediamonds from different mines, which, though they (the diamonds) 
may be called by the same name, have yet an undoubted dissimilarity 
one from the other made up of almost indefinable distinctions of lustre, 
brilliancy, crystallisation, appearance, texture, and general tone. Among 
other things there is the characteristic rippled surface of a Dutoitspan 
diamond as compared with the smooth surface, often with numerous triangular 
indentations, of a Wesselton diamond, and as compared with another from 
Bultfontein. The passages cited at the beginning — which are not really 
independent statements — really understate the case. A person not in daily 
contact with Kimberley diamonds would naturally not be able to recognise 
these differences, but an expert can do so more readily than might be 
supposed. Single stones of every quality, it may be added, do not occur in 
all mines. 
Slight differences have been suspected, and may indeed exist, between the 
lustre of diamonds won from different depths in the same mine. The 
evidence, however, is hardly stronger than that of mental impression based 
