Anthracite coal is the highest-rank coal. It forms by very low- to low-grade metamorphism of bituminous coal. Anthracite is always black-colored, with a glassy texture, and is harder & heavier than the other coals (although it is still relatively soft & lightweight). Unlike lignite and bituminous coal, anthracite is not sooty to the touch. Anthracite burns hotter than other coal types, due to its high carbon content (about 90% C). It also is the cleanest-burning of all the coals.
Anthracite is the rarest variety of coal. The highest concentration of this rock is in Pennsylvanian-aged anthracite coal fields in eastern Pennsylvania, USA.
Anthracite coal (3.9 cm across)