Hobbies And Interests
Types of Coal
Within the U.S., four types of coal have been found in significant enough quantities to support mining operations. Ranked in order of heating efficiency, they include anthracite, bituminous, subbituminous and lignite with the first, type anthracite providing the most heat per equal unit of weight. Anthracite the most heat-efficient type of coal, is pretty well limited to the mountains of northeastern Pennsylvania, while bituminous coal dominates production numbers from other regions of the East, including Kentucky and West Virginia. The remaining two varieties can be found in the western US and Alaska.
Anthracite
Anthracite is a hard and shiny form of coal that gives off the most heat per unit weight and therefore it is the most desirable to mine. Unfortunately, this black rock is the least abundant of all the types of coal, so therefore the price per ton is the highest. Anthracite contains over 87 percent carbon, basing the calculations on a dry ash-free basis.
Bituminous
Bituminous coal is definitely more abundant in the East than anthracite coal. However, the amount of heat released per ton of rock material is less than that of anthracite. In general, carbon content ranges from 77 to 87 percent, just under that of bituminous coal. Over half of the coal mined in the US is found in this form. Bituminous is often referred to as "soft coal," while anthracite is called "hard coal," while in fact their hardness may be about the same.
General Coal Mining
Current coal mining practices in the United States include both surface and underground mining. Surface mines, sometimes called strip mining, can be defined as contour mining, area mining and mountain removal, a recently-developed technique, where the top 600 to 800 feet of mountain are removed and then reclaimed after the coal has been retrieved. Underground mining involves the conventional room and pillar technique of rock removal as well as continuous and longwall mining. The current trend is towards surface mining.