George D. Stonestreet, member of the American Institute of Mining Engineers (MAmIME), was involved in drilling and shaft sinking operations for the gold mining industry at Natalspruit, just south of Germiston, from about February 1896 until at least April 1897. In the latter month he delivered a paper, "Notes on the Black Reef at Natal Spruit", before the Geological Society of South Africa. He was a member of the society at this time and served on its council. His paper, which was published in the society's Transactions (Vol. 2, pp. 53-55), appears to have been the first publication in which the name "Black Reef" was used - a miners' term for an auriferous, dark-coloured arenite and conglomerate in the Transvaal Sequence. Several of his observations and conclusion were criticised by R.L. Cousens* a few months later (Transactions, Vol. 2, pp. 84-86).
Stonestreet was no longer a member of the Geological Society of South Africa in 1899. However, in that year he joined the Chemical and Metallurgical Society of South Africa and was still a member in 1905, after the Anglo-Boer War (1899-1902) and after it had been renamed the Chemical, Metallurgical and Mining Society of South Africa. During the war he appears to have moved to Natal for a while, for in 1901 he wrote to the Natal government about improved methods for handling coal. In 1902-1903 he held the position of inspector of mines at Krugersdorp, in the Transvaal Colony, where he still resided in 1905. By 1903 he was a member of the recently founded South African Association for the Advancement of Science. He was still listed as a member in 1906, but no address was known for him. In 1904 he registered a patent for "improvements in apparatus for disintegrating diamond-bearing earth". That same year he sold two plots in Krugersdorp to the government. In 1908 he applied (unsuccessfully it seems) for the position of government representative of the Transvaal Colony in the United States. He was a Fellow of the Royal Colonial Institute (FRCI).