English: Anthracite coal from the Pennsylvanian of Pennsylvania, USA.

Anthracite coal is the highest-rank of coal. It forms by very low-grade metamorphism (anchimetamorphism) of bituminous coal. Anthracite is always black-colored, with a glassy texture, and is harder and heavier than other coals, although it is still relatively soft and lightweight for its size. In comparison with lignite and bituminous coal, anthracite is less sooty to the touch. Anthracite burns hotter than other coal types, due to its high carbon content (~90% C). It is also the cleanest-burning of all the coal ranks.

Anthracite is a scarce variety of coal. The highest concentration of anthracite on Earth is in the Pennsylvanian-aged coal fields of eastern Pennsylvania, USA. There is still some uncertainty in the details about the origin of Pennsylvania anthracite coal. In Colorado, an anthracite coal deposit occurs next to an igneous intrusion - the anthracite formed by heating from contact or hydrothermal metamorphism. It's been suggested that Pennsylvania anthracite was hydrothermally metamorphosed. The anthracite in Pennsylvania was originally deposited in coal swamps that were relatively high on ancient alluvial plains - those environments are usually not preserved in mountain belts (they get uplifted and eroded). In Pennsylvania, the high alluvial plain facies were downdropped and got preserved, resulting in anthracites representing different facies from those seen in bituminous coal fields.

Age: Pennsylvanian

Locality: unrecorded/undisclosed site at or near the town of Hazelton (probably a coal mine), eastern Pennsylvania, USA