Coal the heat and pressure of deep burial causes the loss of water, methane and carbon dioxide and an increase in the proportion of carbon. Thus first lignite (also called "brown coal"), then sub-bituminous coal, bituminous coal, and lastly anthracite (also called "hard coal" or "black coal") may be formed. The wide, shallow seas of the Carboniferous Period provided ideal conditions for coal formation, although coal is known from most geological periods. The exception is the coal gap in the Permian–Triassic extinction event, where coal is rare. Coal is known from Precambrian strata, which predate land plants—this coal is presumed to
Cannel coal the Drake Oil Well in 1859, made petroleum a cheaper raw material for making kerosene and drove the American oil shale industry out of business. Cannel coal is brown to black oil shale. It comes from resins, spores, waxes, and cutinaceous and corky materials of terrestrial vascular plants, in part from Lycopsid (scale tree). Cannel coal was accumulated in ponds and shallow lakes in peat-forming swamps and bogs of the Carboniferous age under oxygen-deficient conditions. Thus cannel coal seams are shallow and often found above other deposits, while the coal itself, being rich in oils, burns long, with a bright