Lysurn—WMining and Minerals in the Transvaal, etc. 21 
appearance of the blue ground caused much excitement, the 
general opinion being that the yellow ground had become ex- 
hausted ; the yellow ground is, however, neither more nor less 
than decomposed blue ground. 
The diamond-pipes contain a large quantity of foreign mate- 
rial, in the shape of shale, sandstones, dolerite, and granite. The 
sandstones and shales, have evidently fallen in from the sides, 
the granite having been carried up in the ascent of the molten 
material. 
The diamond matrix (kimberlite) consists of garnets (pyrope), 
ilmenite, mica (vaalite), and olivine crystals, constituting a serpen- 
tine breccia. The rock in a state of decomposition has a greasy 
feel. 
In the river diggings, crystals of ilmenite, pyrope, and olivine, 
accompanied by agates and zeolites, are found. Recently, in the 
neighbourhood of Pretoria, a pipe containing kimberlite (?) has 
been discovered. Alluvial diamonds are also being found in the 
south-western border of the Transvaal, in the vicinity of Christiana. 
I may here add that diamonds occur in the strata of all the diffe- 
rent geological periods of South Africa. 
