Early diamond diggers in South Africa introduced some basic methods of recovery that have changed only in scale and sophistication in modern days. At the river diggings, pits were dug down to the gravels which were extracted by pick and shovel. On dry days, gravel was sifted immediately by a man with a round sieve, like an ordinary garden sieve. The sieve had a large mesh so that it retained only pebbles over about an inch across, which after inspection were thrown away. Diamonds were unlikely to be of this size, but any that were could easily be seen and recovered. What passed through the sieve was sifted through a finer sieve to get rid of the sand. Any diamonds the size of sand were not worth recovering. The fraction left the 'middlings' - was taken to the river to be washed in a fine sieve to remove any remaining fine silt and dirt, and the remainder was searched for diamonds. The procedure was not possible on wet days, so the whole of the material dug up was washed while being sieved.
The Long Tom
Australian diggers introduced a form of washer used for alluvial gold which also did some sorting and was known as the long tom. It was a long sloping trough with riffles (small pieces of wood) nailed transversely across it from one end to the other. The gravel was dumped on the higher end and washed down by a stream of water from buckets or a pump. Small and light material including sand was washed down over the riffles, and so were some of the larger lightweight elements, but diamonds were trapped with other heavy minerals. To speed the process, larger stones and pebbles were raked off the long tom and thrown away. The gravel concentrate from the riffes went straight to the sorting table.
The Cradle
The next development, also introduced by gold miners, was probably the cradle, a double wooden box with handles that was stood on flat ground or rock. It was constructed so that the handles rocked the upper part, comprising three sieves from coarse to fine. One is shown in. Mud and gravel from the river was poured into the top, coarsesieve and the cradle rocked while water was poured in. After the mud had gone, the contents of the coarse sieve were emptied on the sorting table and, as it could contain larger diamonds, "loud indeed were the shouts of acclamation and universal was the adjournment to the liquor tent when a diamond was found in this receptacle', according to a contemporary writer. The contents of the middling and fine sieves were then emptied on opposite ends of the sorting bench and sorted. Sieves were constructed from available materials, the simplest being empty gin crates.
The Yankee Baby
A gold digger named J. L. Babe who went to South Africa in 1865, before the Vaal River diamonds were found, as a representative of the Winchester Repeating Rifle Co., joined diggers on the Vaal as related earlier. He decided that current methods were inefficient and, in his own words, 'I then invented a machine which has been universally copied, and which the miners christened the "Yankee baby", and one man could sift with this machine as much in ten hours as four could do with the common sifter.' By selling the machine and by using it himself on the diggings, J. L. Babe was so successful that he was able to retire to America in 1873. The baby comprised two sieves, one above the other. The main one was in a large rectangular frame hung from four rawhide thongs or light chains from four posts planted in the ground. It was fed through a smaller sieve about 2 ft (61 cm) square with a mesh that allowed through it stones up to about } in. (13 mm) across. The total effect was that the larger material was discarded at one end of the baby and the fine tailings underneath. Off the other end came the middlings, which were then washed and sorted. Babe had his machine made in Colesberg. shows a rocking screen made at some later date. Washing could be carried out before or after screening, depending upon the deposit - how much fine material or earth was in it - and upon the availability and cost of water.
The Trommel
The baby was superseded on many diggings by the cylinder or trommel. Wire netting or punched iron sheet was used to make a cylinder several feet long. The cylinder was revolved on an axle by a handle and could be sealed with a lid at each end. It was partly filled with gravel that had already been screened and rotated while immersed in a trough of water, if possible. As it provided some security and saved labour, it was popular with diggers. Two versions are shown in.
Concentrating in Water
Water was used as a means of concentrating the heavier fraction of the gravels. The term concentrating means separating the material of higher relative density. This heavier fraction of gravel is called the concentrate, and obviously most concentrates can be further concentrated. The sieving method introduced into the diamond fields was already known to gold miners and is still in use in various parts of the world by both gold and diamond miners. Deposit that has been screened and washed is emptied in a convenient quantity into a sieve, which is about 30 in (76 cm) across and has a bottom of fine mesh. The sieve is held in a tub of water or in the river, where it is sharply twisted one way then the other a few times and then moved more gently up and down in a jigging motion. The actions are repeated until the lighter gravels come to the top of the sieve and the heavier ones are concentrated in the middle at the bottom. Sieves were, and still are by independent diggers, used in two and threes to grade concentrate, dividing it into two or three groups for picking The digger uses a large metal 'washer' between cach pair of sieves so that the heavier and smaller elements from the centre of the upper sieve are passed through to the lower one.
The sieve is liſted out of the water and taken to the picking table where it is deftly turned over and the contents dumped on the table like a child making a mud pic. When the sieve is lifted off, the gravel is left, shining wet, in the shape of a large flat cake. The picker examines the stones on the top in the middle of the pile, and picks out any diamond crystals. Then, to make sure that no diamonds have remained in the rest of the gravel, he goes through the 'cake' of gravel, a slice at a time. To do this, he uses a home-made tool, usually a triangular piece of iron or aluminium about 6 in long by 3 in or less wide (152 X 76 mm). With the tool, he cuts off a section of the gravel and spreads it across the sorting table, examining the multicoloured concentrate for diamonds. Then he sweeps this layer on to the ground and takes another section of the heap until it has gone.
The Picking Table
The picking table was at first nothing more than the top of a packing case standing on a heap of gravel at which the digger crouched, sat or knelt. Then packing cases were made into rough tables, perhaps covered by sacking and with strips nailed along three sides to prevent gravel from rolling off. Iron sheet from an old enamelled advertisement or flattened tin containers was nailed on the top and the table top sloped so that water did not pour over the digger's knees when gravel was tipped on to the table in front of him. More enterprising diggers made their tables into booths with top and canvas sides to give shade for sorting Exactly the same methods are used by individual diggers today, although the sieve may be a little different. In Guyana, for example, a cone-shaped pan, like a metal dustbin top, is used instead of a sieve. At Nooitgedacht, on the Vaal River banks, the method has not changed at all. In the later days of the river diggings, rotary washing pans were introduced. They had been developed at the dry diggings as described on the following pages. Hand-operated rotary washing pans are also still in use today on individual claims.
Mining at the Dry Diggings
When the dry diggings were first discovered, they were thought to be the same kind of deposits as the river ones and the same methods of recovery were employed. It was naturally supposed that the deposits were of only limited depth, and claims were allowed next to each other, just like those by the rivers. By the time that the 'New Rush' (now the Kimberley Big Hole) was found in 1871, it was known that deposits went down to a considerable depth, so it was decided that each claim would contribute a 71 ft strip (2-3 m) which would not be worked for the general benefit. This resulted in a series of roadways 15 ft (4:6 m) wide and 45 ft (13-7m) apart. The idea was practicable at first, but as soon as the claims were dug deeply with almost vertical sides, the roads began to fall in. The whole area was weathered yellow ground, which became very friable as it weathered even further after exposure to the air. The ground being mined was dug with picks and shovels and loaded into sacks, which were carried by labourers up steps cut in the side of the claim and emptied by the side of the road. The sacks were taken to the edge of the mine and the ground broken up, screened and sorted there. Some claims had sloping ramps up which hand trucks of ground were pushed. As the mine grew deeper, a crude system of benches evolved, each claim having terraces up to the road. The ground was thrown up to each by labourers until it reached the road as many as five levels higher. Then diggers started hauling up ground in buckets by driving posts with pulleys and ropes into the roads. Scotch carts, which could be tipped up, were used to take the ground from the roads to the edge of the Big Hole, but animals fell into the claims and had to be slaughtered. Some diggers tried to bridge crumbled roads ‘at enormous expense'. Views of the Big Hole can be seen in.
