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
Frank (given name) Frank (given name) Frank is a masculine given name. Ultimately from the Germanic tribal name of the Franks, in the early medieval Frankish Empire, the status of being "a Frank" became synonymous with that of a free man; hence also the English adjective "frank" (Middle English, from Old French "franc", 12th century). Use as a given name seems to arise already in the Carolingian period; the Old High German form "Francho, Franko" is on record from the 8th century. While "Frank" is a given name in its own right, in fact reflecting the Old Frankish form "*Frank", the given name