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DIAMOND MINES OF SOUTH AFRICA 255
ginning,
like the Kimberley, it was very rich, running at times over two carats
to the load; it is now about .30 of a carat. The Roberts-Victor also,
which opened up with a yield of .91 in May, 1906, dropped to an average
of .536 for the year 1907. Part of this apparent deterioration is
undoubtedly due to the fact that when a mine is opened, especially if
the entire chimney is under one management, the most promising spots
are worked first, whereas when the mining is deeper, not only must the
entire area be worked, but the leftover part of the higher levels have
to be taken down and included. The showing of the Premier and the
Roberts-Victor illustrates the probable conditions of the Kimberley
when it was first opened, but which did not appear, because there was
no exact report of entire results, but uncertain returns from some of
the many owners of parts of the chimney. It will be noticed that most
of the. mines eventually settle down to a yield of from one-quarter to
one-half of a carat per load, especially after the open cut is
abandoned and underground working begins, when there is not the same
opportunity to make selections, but good and bad sections are worked
together.
A
number of true pipes have been discovered. In the eighties already,
some fifteen were known in the Kimberley district and the Orange Free
State. Many of them, however, yielded but little, and are comparatively
unknown. There are several other mines in addition to the five mines of
the De Beers Consolidation, in the Kimberley section. The Peizer, the
New Weltevrede and the Frank Smith, north-west of Kimberley. In the
Orange River Colony are the Jagersfontein, Lace,
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