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
Calgon Carbon pond and aquarium cleaning, and removal of impurities during the manufacturing process of vitamins. The company also serves "industrial processes" applications such as liquid chemicals, catalyst support, gas and water processing, ultrapure water, and bio-based chemicals. Activated carbon, which is a small form of carbon with a large pore structure that can remove impurities, was one of the first products produced by the company in the 1940s. Initially manufacturing granular activated carbon (GAC), the company also began producing forms such as powdered, pellets, and later cloth. Pittsburgh Coke and Chemical introduced an early activated carbon system to decolorize sugar in