There are several highly mineralized areas in the country.
In a general way it is supposed that the lands lying between the lower St Paul's river and the Sierra Leone frontier are not much mineralized, except that in the vicinity of river mouths there are indications of bitumen.
Similarly there is a difference of opinion as to the conditions under which the organisms have been mineralized, some holding that the process has taken place at a high temperature and under great pressure; but the lack of practical evidence in nature in support of these views has led many to conclude that petroleum, like coal, has been formed at moderate temperatures, and under pressures varying with the depth of the containing rocks.
Vryheid (2287) is in the centre of a highly mineralized district.
In the older formations the phosphates tend to become more and more mineralized by chemical processes.
Many fossils are mineralized with pyrites, which has evidently been reduced by the action of decomposing organic matter on a solution of ferrous sulphate, or perhaps less directly on ferrous carbonate dissolved in water containing carbonic acid, in the presence of certain sulphates.
It is highly mineralized, next to gold, copper, found near the Limpopo (where is the Messina mine) being the chief metal worked.
Near the crest of anticlines is commonly an enriched portion of the ground in mineralized districts; and, in the case of water supply, the tilt of the strata determines the direction of the underground flowage.
The lias shales of Whitby contain blocks of semi-mineralized wood, or jet, which is black with a resinous lustre, and a fibrous structure.