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
J & A Brown South Wales. From that time the surviving member of the Brown family Stephen Brown served as a director in the new public company. In 1960, JABAS merged with Caledonian Collieries Limited to form Coal & Allied Industries Limited. After this merger, JABAS become the subsidiary company that carried out the mining operations of Coal & Allied until being renamed Coal & Allied Operations Pty Ltd in 1980. As of 2013, Coal & Allied Operations Pty Ltd is a subsidiary of Rio Tinto Coal Australia. J & A Brown J & A Brown was an privately owned Australian coal family firm