Petroleum and natural gas also occur in the plateau rocks in great quantities.
- The state's great mineral wealth is in coals of various kinds, petroleum, and natural gas.
Petroleum was collected for use in the most remote ages of which we have any records.
As early as 1804, Humboldt expressed the opinion that petroleum was produced by distillation from deep-seated strata, and Karl Reichenbach in 1834, suggested that it was derived from the action of heat on the turpentine of pine-trees, whilst Brunet, in 1838, adumbrated a similar theory of origin on the ground of certain laboratory experiments.
Deposits of copper, tin, iron and tungsten have been discovered, and a variety of other mineral products (graphite, mica, spodumene, coal, petroleum, &c.).