23 
geological series than the Karoo beds, which lie on the floor of 
the valley, and are pierced and covered by greenstone and 
amygdaloid lavas, (2) The materials of some of the Karoo beds, 
and, (3) The metamorphic rocks of the Upper Vaal which 
occur with gneiss, mica slates, and quartz, bearing in this re¬ 
spect an analogy to some of the diamond-producing rocks of 
Brazil. 
In relation to diamantiferous indications, the diggers have 
always regarded garnet and tourmaline as associates of the 
diamond, and this opinion is borne out by facts. In the Orange 
Kiver Kepublic the mineral is found in isolated spots, called 
Pans,” which are basin-like hollows, being in ^vet seasons 
more or less fllled with saline water, and in dry seasons pre¬ 
senting a saline eiflorescent surface. In these localities the 
favoured accompaniment of the diamond is a fine clayey talcy 
detritus, full of garnet, tourmaline and corundum, and of a 
greenish, or, when iron is present, red colour. This material. 
Dr. Shaw considers, the correlative of itacolumite. As these 
indications exist throughout the whole of the diamond- 
producing region. Dr. Shaw goes on to say that he is disposed to 
think, that the talcose slate which produced the detritus, was 
the original matrix of the diamond, and this rock was one of 
the series of the metamorphic rocks—gneiss, mica-schist, &c. In 
the Pans,” fragments of these have been preserved. But the 
inference is that the original diamantiferous rock has ex¬ 
tended throughout the whole of this part of S. Africa. This 
and the associated rocks were disturbed by the greenstone 
upheavals which probably occurred at various times. During, 
and subsequent to these disturbances, was the great lake-period 
of S. Africa, when the immense deposits of lacustrine forma¬ 
tions were made. The ancient rocks yielded to denudation 
and wearing, in some cases went towards the formation of trap 
conglomerates, and generally have found their way to the 
nuclei of the present period, the Vaal river and those of its 
tributaries, the Beit and the Hart, and the pans and sheltered 
spots, where isolated diamond deposits exist. 
But, if even the exact site of the matrix was accurately de¬ 
cided, it is questionable whether it would be more profitable to 
