Science Fact Finder | Energy - What Types Of Coal Are There?

What types of coal are there?

There are four types of coal, each of which are produced by pressure, temperature, and chemical processes that occur over long periods of time.

The early stages of coal formation yield lignite, a dark brown, woody-textured substance. With increased pressure, lignite is converted into a harder, blacker substance called sub-bituminous coal. Under still greater pressure, a somewhat harder coal called bituminous coal ("soft coal") is produced. Intense pressure changes bituminous coal into anthracite, the hardest of all coals.

Sources: Brady, George S. Materials Handbook, 13th ed., p. 207; World Book Encyclopedia, vol. 4, 716-17.

Join eNotes

The above is a free excerpt. Get total access to this content with the:

eNotes Pass