What the Vredefort impact achieved, however, was to distort the Witwatersrand basin in such a way that the gold-bearing rocks were brought to the present erosion surface in Johannesburg, on the Witwatersrand, just inside the rim of the original 300 km (190 mi) diameter crater caused by the meteor strike. The discovery of the deposit in 1886 launched the Witwatersrand Gold Rush. Some 22% of all the gold that is ascertained to exist today on Earth has been extracted from these Witwatersrand rocks. Mantle return theories
Notwithstanding the impact above, much of the rest of the gold on Earth is thought to have been incorporated into the planet since its very beginning, as planetesimals formed the planets mantle, early in Earths creation. In 2017, an international group of scientists, established that gold "came to the Earths surface from the deepest regions of our planet", the mantle, evidenced by their findings at Deseado Massif in the Argentinian Patagonia. Occurrence
On Earth, gold is found in ores in rock formed from the Precambrian time onward. It most often occurs as a native metal, typically in a metal solid solution with silver (i.e. as a gold/silver alloy). Such alloys usually have a silver content of 8–10%. Electrum is elemental gold with more than 20% silver, and is commonly known as white gold. Electrums color runs from golden-silvery to silvery, dependent upon the silver content. The more silver, the lower the specific gravity.
Haemophilus meningitis is a form of bacterial meningitis caused by the Haemophilus influenzae bacteria. It is usually (but not always) associated with Haemophilus influenzae type b. Meningitis involves the inflammation of the protective membranes that cover the brain and spinal cord. Haemophilus meningitis is characterized by symptoms including fever, nausea, sensitivity to light, headaches, stiff neck, anorexia, and seizures. Haemophilus meningitis can be deadly, but antibiotics are effective in treating the infection, especially when cases are caught early enough that the inflammation has not done a great deal of damage. Before the introduction of the Hib vaccine in 1985, Haemophilus meningitis was the leading cause of bacterial meningitis in children under the age of five. However, since the creation of the Hib vaccine, only two in every 100,000 children contract this type of meningitis. Five to ten percent of cases can be fatal, although the average mortality rate in developing nations is seventeen percent, mostly due to lack of access to vaccination as well as lack of access to medical care needed to combat the meningitis. Symptoms and signs
Possible symptoms of Haemophilus meningitis include:
Nausea or vomiting
Fever
Headache
Sensitivity to light
Seizures
Anorexia
change in mental status, such as irritability
stiff neck

Risk factors
While the Haemophilus influenzae bacteria are unable to survive in any environment outside of the human body, humans can carry the bacteria within their bodies without developing any symptoms of the disease. It spreads through the air when an individual carrying the bacteria coughs or sneezes.