From these surface exposures the basin dips extensively, requiring some of the mining to occur at depths of nearly 4,000 m (13,000 ft), making them, especially the Savuka and TauTona mines to the south-west of Johannesburg, the deepest mines on earth. The gold is found only in six areas where archean rivers from the north and north-west formed extensive pebbly Braided river deltas before draining into the "Witwatersrand sea" where the rest of the Witwatersrand sediments were deposited.The Second Boer War of 1899–1901 between the British Empire and the Afrikaner Boers was at least partly over the rights of miners and possession of the gold wealth in South Africa. During the 19th century, gold rushes occurred whenever large gold deposits were discovered. The first documented discovery of gold in the United States was at the Reed Gold Mine near Georgeville, North Carolina in 1803. The first major gold strike in the United States occurred in a small north Georgia town called Dahlonega. Further gold rushes occurred in California, Colorado, the Black Hills, Otago in New Zealand, a number of locations across Australia, Witwatersrand in South Africa, and the Klondike in Canada. Grasberg mine located in Papua, Indonesia is the largest gold mine in the world. Extraction and refining
Gold extraction is most economical in large, easily mined deposits. Ore grades as little as 0.5 parts per million (ppm) can be economical. Typical ore grades in open-pit mines are 1–5 ppm; ore grades in underground or hard rock mines are usually at least 3 ppm.
This has been recognized in the settings of certain cancers (such as myeloid leukemia), lung infections, or environmental exposure to dusts or chemicals, such as nickel.Although the cause of PAP was not originally understood, a major breakthrough in the understanding of the cause of the disease came by the chance observation that mice bred for experimental study to lack a hematologic growth factor known as granulocyte-macrophage colony stimulating factor (GM-CSF) developed a pulmonary syndrome of abnormal surfactant accumulation resembling human PAP.The implications of this finding are still being explored, but significant progress was reported in February 2007. Researchers in that report discussed the presence of anti-GM-CSF autoantibodies in patients with PAP, and duplicated that syndrome with the infusion of these autoantibodies into mice.Familial or sporadic inactivating mutations in one of the two parental GATA2 genes produces an autosomal dominant disorder termed GATA2 deficiency. The GATA2 gene produces the GATA2 transcription factor which is critical for the embryonic development, maintenance, and functionality of blood-forming, lympathic-forming, and other tissue-forming cells. Individuals with a single GATA2 inactivating mutation present with a wide range of disorders including pulmonary alveolar proteinosis. GATA2 mutation-based pulmonary alveolar proteinosis is associated with normal levels of GM-CSF and commonly improves or is avoided in afflicted individuals who successfully receive a hematopoietic stem cell transplantation. Genetics
Hereditary pulmonary alveolar proteinosis is a recessive genetic condition in which individuals are born with genetic mutations that deteriorate the function of the CSF2 receptor alpha on alveolar macrophages.