Had diamonds been formed in this rock, and the rock crushed, the brittle diamond would not, in my opinion, have escaped being also crushed. It seems a more feasible theory that the rock when first elevated was in a heated state, and brought into contact with water then covering the land, and the sudden cooling caused its sudden disintegration, and that the diamonds and other materials foreign to it got mixed with it subsequently. However, in either case, the diamonds and other materials contained therein would still have to be accounted for, and it does not appear probable that these should have all been formed with or within one single rock, or that they are all of the same period and were elevated at one and the same time.
If diamonds were formed by heat, it was not in the Kimberley mine, as the shale walls and the agglomerate within the mine show no signs of having there been subjected to any great heat; on the contrary, water and air seem to have been here the active agents.
From the foregoing extracts it will be seen that no theory as to the formation of the diamond hitherto advanced is completely, if at all satisfactory, and the mystery, if penetrable, must be left to the geologist of the future.
GEOLOGY, FOSSILS, Etc.
DESCRIPTION OF PLATES.
[PLATE I.]
Fig. 1. Scale ¹⁄₆₀ inch to the foot. This represents a section of a shaft sunk by the Kimberley Mining Board, at the N. E. of and about 700 feet from the then margin of the mine. The section was taken by Mr. Geo. Jas. Lee, a gentleman who was at one time chairman of the mining board, and who, when it finally decided to abandon the shaft named in 1878, took the section of which the accompanying diagram or illustration gives an accurate representation.
The dip of the strata is about 2°.5 N. N. W.
(a) Represents a heap of diamondiferous débris from the yellow ground of the mine, 14 feet in depth.
(b) Surface red sand, 6 feet thick. There was no calcareous tufa underlying the red sand here, as is usually the case within the mine proper and its immediate vicinity.
(c) Jointed trap, or blue whin, 15 feet.