According to the rootsweb history, Aaron was the first partner of Harry Barnato in the diamond business. For those of you who may not know, I wrote the biography of Barney Barnato - King of Diamonds, the Life of Barney Barnato. ISBN 9781505523409.
Anthony Davis
Note: In April 1867 the children of a Boer farmer had picked up an unusually pretty pebble on the banks of the Orange River. It was a fine diamond of 20 carat. Two years later, a much larger stone was found near the Vaal by a shepherd boy. It was the "Star of South Africa". Several 1000 prospectors were soon scouring the river banks for diamonds but the major finds were made on the dry diggings inland. Two mines were to be public diggings: the De Beer Mine and the Colesburg Kopje, which became the Kimberley Mine. Other major mines were on the Dutoitspan and Bulfontein farms. Amongst the rush of prospectors from all parts of Europe in 1870 was Aaron van Praagh. He set up in partnership with Harry Barnato, as diamond buyers, and "van Praaghs" became one of the leading firms. Harry's brother Barney, in due course became on of the two largest mine owners, the other being Cecil Rhodes and these two combined their resources to form the De Beers Consolidated Mines ltd in 1888. De Beers soon came to control 95% of the world production of diamonds. Aaron was a load office clerk, and so after his adventurous years in the diamond fields he had returned to London and settled into a humdrum job. Joseph van Praagh went to Beira, Portuguese East Africa, in 1891 and walked 300 miles to Salisbury, Rhodesia with his cousin Julius Altman, where he became the manger of the Manios Trading Company. He served in the military volunteers during the native rebellion in 1896, became the third mayor of Salisbury in 1900, soon after he went to Griqualand West, which was the territory where the diamond mines were. He did not marry and was a very religious Jew and an active Freemason