150 THE DIAMOND MINES OF SOUTH AFRICA
I
cannot accept the contention that the boulders came from any strata
through which the pipes have been formed, unless these strata lie very
deep and below the quartz porphyry.
The
conglomerate which lies between the shale and mela-phyre is only a few
feet thick, ten to fifteen at most, and does not contain large boulders
such as are found in the blue ground ; besides, the quantity of
boulders or conglomerate which could have been contained in the area of
the mine would not have supplied the amount of stones already found in
the blue ground. These must, therefore, have come up from below with
the diamond-bearing ground. If the boulders came from the Dwyka
conglomerate, it must lie very deep beneath the surface, for nothing of
the kind has been found at a depth of over twenty-one hundred feet.
Professor
Bonney says above that the statement of the occurrence of diamonds in
itacolumite* needs corroboration. There is no doubt in my own mind that
diamonds in Brazil have been found in itacolumite, and the consensus of
opinion is that it is not the original matrix, but that the diamonds
were washed from their volcanic origin and became bedded in this
sandstone when it was being formed.
I
have been frequently asked, " What is your theory of the original
crystallization of the diamond ?" and the answer has always been, " I
have none ; for after seventeen years of thoughtful study coupled with
practical research I find that it is easier to ' drive a coach and
four' through most theories which have been propounded than to suggest
one which would be based upon any more unassailable data." All that can
be said is that in some unknown manner carbon, which existed down deep
in the internal regions of the earth, was changed from its black and
uninviting appearance to the most beautiful gem which ever saw the
light of day.
1 Brittle quartz sandstone of slaty (schistose) character. — Heusser.
