The ground was discovered to be diamondiferous in 1897, but it was not until 1903, when mining began on the Premier mine, situated 20 m.
Besides the Pretoria fields there are diamondiferous areas (alluvial diggings) in the Bloemhof district on the Vaal river north-east of Kimberley, and in other regions.
The diamondiferous areas at Kimberley and in the Pretoria district are likewise the richest known.
It takes ten acres of Karroo to feed a sheep, but it was now seen that a few square yards of diamondiferous blue ground would feed a dozen families.
Tin is also mined in Katanga, but up to 1921 little had been done to exploit its iron and gold deposits and diamondiferous areas.