http://www.minersmuseum.com/history-of-mining/coal-formation/

There are four stages in coal formation: peat, lignite, bituminous and anthracite. The stage depends upon the conditions to which the plant remains are subjected  ...

http://www.coaleducation.org/q&a/how_coal_formed.htm

Home, Kentucky Coal, Modern Technology, Teacher's, Fun Stuff, Site ... or conditions under which these coals were formed: anthracite coal, bituminous coal ,

https://www.quora.com/What-is-the-process-of-the-formation-of-anthracite-coal

Anthracite Anthracite is the highest rank of coal. It has a carbon content of over 87 % on a dry ash-free basis. Anthracite coal generally has the ...

https://en.wikipedia.org/wiki/Anthracite

Anthracite, often referred to as hard coal, is a hard, compact variety of coal that has a submetallic luster. It has the highest carbon content, the fewest impurities, ...

https://geology.com/rocks/coal.shtml

Coal is a biological sedimentary rock that forms from plant debris.

https://www.britannica.com/science/anthracite

Anthracite: Anthracite, the most highly metamorphosed form of coal. ... to 250 °C ( about 340 to 480 °F) are thought to be necessary for the formation of anthracite.

https://www.nationalgeographic.org/encyclopedia/coal/

Dec 22, 2012 ... Bituminous coal is formed under more heat and pressure, and is 100 ... Because anthracite is a high-quality coal, it burns cleanly, with very little ...

https://courses.lumenlearning.com/geo/chapter/reading-coal-2/

The harder forms, such as anthracite coal, can be regarded as metamorphic rock ... for coal formation, although coal is known from most geological periods.

https://energyeducation.ca/encyclopedia/Coal_formation

Jan 4, 2019 ... The formation of coal takes a significant amount of time (on the ... coal, then bituminous coal, and finally the highest quality anthracite coal.

http://epcamr.org/home/content/reference-materials/coal-types-formation-and-methods-of-mining/

The fourth and final phase results in the formation of anthracite (hard coal). If anthracite coal was placed under more heat and pressure, it would eventually be  ...