Anthracite

Coal waste pile west of Trevorton, Pennsylvania far shot 2

Ibbenbueren Anthracite

Anthracite coal (Photo by John Mortimore)

Coal plant, Madrid c. 1935

Working together for Victory. Anthracite is a "fighting fuel." America needs it now. - NARA - 534850

Anthracite is a hard, compact variety of coal that has a submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the highest ranking of coals. Anthracite is the most metamorphosed type of coal (but still represents low-grade metamorphism), in which the carbon content is between 92% and 98%. The term is applied to those varieties of coal which do not give off tarry or other hydrocarbon vapours when heated below their point of ignition. Anthracite ignites with difficulty and burns with a short, blue, and smokeless flame.

Characteristics

Anthracite differs from ordinary bituminous coal by its greater hardness (2.75–3 on the Mohs scale), its higher relative density of 1.3–1.4, and luster, which is often semi-metallic with a mildly brown reflection. It contains a high percentage of fixed carbon and a low percentage of volatile matter. It is also free from included soft or fibrous notches and does not soil the fingers when rubbed. Anthracite's color ranges from black to a metallic grey and is often referred to as "hard coal."

Formation

Anthracite is formed from the accumulation of plant debris in swamp environments. This organic matter, with the aid of pressure and heat over millions of years, undergoes chemical and physical changes, leading to the formation of peat, and upon further metamorphism, lignite, bituminous coal, and finally, anthracite. This process, known as coalification, increases the carbon content and decreases the volatile matter content. Anthracite formation is often associated with the geological regions known as coal basins, which are extensive areas that have undergone subsidence, allowing for thick layers of plant debris to accumulate.

Uses

Historically, anthracite was used for residential and commercial heating, due to its high energy content and clean burning properties. It is also used in the metallurgical industry as a reductant for smelting iron ore in a blast furnace, due to its high carbon content and because it burns at a high temperature with a very clean flame. In addition, anthracite is used in water filtration systems, due to its ability to absorb impurities and because it is a high-density filter media that does not float away.

Mining

The mining of anthracite began in the early 19th century, primarily in the United States and Wales. The United States, particularly Pennsylvania, has the largest reserves of anthracite. Mining methods have evolved from underground mining to open pit mining, and the environmental impact of mining has been a concern, with efforts made to restore land after mining and to reduce the release of mining by-products into the environment.

Environmental Impact

While anthracite is cleaner burning than other forms of coal, it still contributes to air pollution and greenhouse gas emissions when burned. However, its high energy content means that less coal needs to be burned to produce the same amount of heat or electricity, which can reduce the overall impact on the environment.

Conclusion

Anthracite plays a significant role in both the energy industry and in metallurgical processes. Despite its cleaner burning properties, the environmental impacts of mining and burning anthracite must be carefully managed. As the world moves towards more sustainable energy sources, the use of anthracite may decrease, but its role in industrial processes and in regions where it is abundantly available will likely continue.