There are two competing ideas of how platinum deposits formed: the first involves gravity-induced settling of crystals on the chamber floor, while the second idea implies that the crystals grow in situ, directly on the floor of the magmatic chamber. Researchers have established that the crystals grow in situ, with its high platinum status being attained while all its minerals were crystallizing along the cooling margins of the magma chamber.
Click here for original story, The secret of platinum deposits revealed by field observations in South Africa
Source: ScienceDaily