Sherman and MacMurphy • Origin, Nature and Uses of Coal 



207 



Allan Sherman and Allen B. MacMurphy 



Origin, Nature and Uses of Coal 



Reprinted with the permission of the authors 

 from Facts About Coal, U.S.D.I., Bureau of 

 Mines, 1955. 



HOW COAL WAS FORMED 



Although coal is commonly thought 

 of as a mineral and is classed as a min- 

 eral resource, it is not a mineral in the 

 sense that stone, iron ore, and other 

 substances are. Tliis is because coal is 

 of organic origin, which means that it 

 was formed from the remains of living 

 things— trees, shrubs, herbs, mosses, 

 algae and vines— that grew millions 

 upon millions of years ago, during 

 periods of widespread uniformly mild, 

 moist climate. During those periods, 

 there was heavy growth of vegetation 

 in forested swamps and bogs. Century 

 after century, this vegetation died and 

 accumulated. Buried to a gradually 

 increasing depth each year by new ac- 

 cumulations, the remains of roots, 

 trunks, branches, and leaves changed 

 gradually to peat, just as decaying 

 vegetable matter is doing today in the 

 Dismal Swamp of \'irginia and North 

 Carolina, and in smaller swamps and 

 bogs in manv states. 



Peat is the first step in changing 

 organic matter into coal. In a block of 

 peat you can often see, with the naked 

 eye, the woody fragments of stems. 



roots, and bark. When dried, peat can 

 be burned; but in this countr}', because 

 better fuels are plentiful, it is used 

 chiefly as an ingredient of fertilizers, 

 as a soil conditioner, and, to some ex- 

 tent, as a packing material for plants, 

 fruits, and vegetables. 



As the peat substance was buried, 

 it was cut off from the oxygen in the 

 air, and this prevented rapid decay of 

 its organic matter by slowing bacterial 

 action. The weight of more vegetation 

 falling on the peat helped to compress 

 and solidif}^ it. So did the weight of 

 water if the peat deposit sank below 

 the sea, as often happened. Sometimes 

 mineral sediments settled from muddy 

 flood waters during the period when 

 the vegetable matter was accumulating, 

 and then what we now call "partings," 

 or layers of shale, were formed in the 

 coal vein. During the coal-forming 

 period, the swamps were flooded b\- sea 

 water for a long time; and earthy sedi- 

 ments were deposited in thick beds 

 over the peat, further compressing it 

 and starting the coal-making process, 

 which is called "coalification." 



Coalification was cxtrcmclv slow 

 when it depended mainly upon the 



