Poor surface claims often became changed to rich ones owing to the vicinity of a wall of floating reef, and it was often found that after months, even years, had been spent in working down a claim unprofitably, it would suddenly alter to a payable or probably a rich one, for at a varying depth alongside the floating reef, or after the reef had been removed, I have many a time known a change for the better to take place, and the owner, who had been almost reduced to the verge of bankruptcy, to be soon set upon his legs again.
Some of the claims at the west of the mine never paid the expense of working at the surface, nor even in the yellow ground below, and remain absolutely worthless to this day, although the blue ground has been reached, worked, and tested. About five claims in the very centre of the mine were proverbially poor, vast quantities of erratic boulders being mixed up with, and in some cases almost displacing, the yellow and blue ground. Some of these fragments of rock were of immense size, weighing thousands of tons, and at the same time were so solid that they had to be blasted to pieces. They consisted for the most part of dark and light colored shales, whinstone or basaltic boulders, and large masses of fine-grained micaceous sandstone, containing fragments of coal and remains of a fossil reptile. Much lignite in large stems and branches was also found amongst the boulders and in the blue. When this floating reef was removed, many feet of unprofitable blue had also to be removed before payable ground was reached, but when all the poor ground was taken away, the junction of which with the richer ground was very perceptible by a change of color, the remaining blue did not differ in average return of diamonds from the rich claims surrounding it.
Several remarkable detached boulders were found. One in No. 3 road south, of such a large size that it covered the two claims of a well-known digger named Olsen, Nos. 136 and 166. It was a pudding-stone, its chief constituent being grayish white crystals and fragments of feldspar, transparent and translucent, concreted together with carbonate of lime. This “erratic” contained also nodules of quartz, crystals of iron pyrites, and many small cavities filled with diamondiferous soil of a light brownish gray color.
Again in Nos. 8 and 9 roads south, there was an isolated basaltic boulder, nearly round, of gigantic proportions. It almost filled up claims 432 and 433 in road No. 8, and claims 462 and 463 in road No. 9, and measured in diameter 70 feet, 35 feet in the yellow ground and the same in the blue below. It was much decomposed, and large flakes or layers frequently fell away into neighboring claims, causing many lawsuits. The claim-holders burrowed round this piece of rock as long as they possibly could, but at last they had to face the expense of breaking it up and removing it. The upper portion of this stone in the yellow ground had a yellow, and the lower portion in the blue a blue tint, showing that the same cause which affected the coloring of the diamondiferous ground also affected the imbedded “erratic.”
The floating reef proper in the Kimberley mine extended from the southeast to the northwest; but there was also a large patch of floating reef running north and south in No. 8 road.
The width of this reef varied from five feet to forty feet, and the average depth was about 200 feet. It was formed of a light olive-gray colored laminated shale, with a few rounded stones and angular pieces of basaltic rock, as well as occasional fragments of fine grained sandstone. These walls of shale were for the most part compact and unbroken, with a few straggling pieces of various sizes in the immediate vicinity. This rock was totally different from any forming the walls of the mine, and no similar shale has been recognized to my knowledge in any part of the country.
At the southwest of the mine, in ground at that time belonging to Messrs. Lewis and Marks, there was a large floating reef composed of disintegrated igneous rock, resembling dolerite, which commenced near the main reef, and which jutted out to a distance of 120 feet in a northwesterly direction; this was a different rock from that forming the walls of the mine or any discoverable in the adjacent country.
Veins or seams of crystallized carbonate of lime frequently run through the blue ground in all directions, in sheets more or less broad, and varying in thickness from a mere trace to two or three inches. The calcite is covered with a coating of a grayish white substance, very soapy to the touch, resembling steatite. Some of this lime contained cavities, having a fine deposit of iron pyrites which exhibited the most brilliant iridescence conceivable. One specimen which I saw was so beautiful that it was thought even worthy of presentation to royalty, and the owner gave it to Captain Harrell (formerly Cis-Molappo commissioner) for the purpose, but through some blundering or other it never reached its destination. Eventually, I believe, Captain Harrell, with the consent of the donor, caused it to be deposited in the South Kensington Museum.
When Sir Henry Barkly was here in 1872 this was shown him, and he confessed it to be unique, in his opinion, and the prettiest specimen of the kind he had ever seen.
When a wall or block of blue ground is dressed down and left standing with such a vein—or greasy slip, as it is termed—in it, it becomes highly dangerous, as all above the vein (at times an immense mass) is liable to come down without a moment’s warning.