ON THE HIS TOBY OF THE DIAMOND 7
mentioned
those of Prof. E. Cohen, of Mr. Hudleston, and of Mr. Dunn. Mr.
Hudleston' holds that the matrix of the diamond was a sort of volcanic
breccia, 'which was made hydrous at a considerable depth and ejected in
a wet state accompanied by steam, like the product of a mud volcano.
The earlier theories as to the origin of the diamond have, in the light
of new facts, quite given way to the theory that the diamonds belong to
and are part of the matrix in which they lie, and that this matrix is
in some way of volcanic origin, either in the form of mud or ashes or
lava.
As
the geology of the region has been described by many observers, it may
suffice to say that the diamond-bearing pipes penetrate strata of
Triassic age which are known as the Karoo beds. Griesbach 2 and Stow3
in 1871 showed that this Karoo formation was penetrated by great .
iiiterstratined sheets of so-called dolerite, melaphyre and
amygdaloidal melaphyre, and that below the series of stratified rocks
fundamental clay slates and gneisses or granite occurred, which latter
came to the surface in Natal and the adjoining regions. The intrusion
of the dolerite sheets in the Karoo beds is held to have occurred in a
subsequent part of the Triassic period known as that of the Stormberg
beds.4 As Professor Rupert Jones5 and others have
shown, the Kimberley shales belong to the lower Karoo formation. The
diamond-bearing pipes penetrating and enclosing fragments of all these
formations are thus clearly of upper Triassic or post-Triassic age.
1 now come to the description of the rocks which, through the courtesy of Mr. T. Hedley, in charge of the
