Pakistan is also a major producer of Bituminous coal, Sub-bituminous coal and Lignite. Softer bituminous coal replaced anthracite for steel production. The Appalachian Mountains contain major deposits of anthracite coal as well as bituminous coal. Additionally, substantial coal deposits are found in Alaska's bituminous, sub-bituminous, and lignite coal basins. Substantial deposits of bituminous, subbituminous, and lignite coal are found in the state. The even softer sub-bituminous and lignite coals overtook bituminous in the 2000s. Energy needs are also met by importing bituminous and anthracite coal and crude petroleum. Anthracitization is the transformation of bituminous coal into anthracite. The burning of harder, older anthracite and bituminous coal typically produces Class F fly ash. It is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. It contains some sedimentary rock and bituminous coal. Hot concentrated sulfuric acid oxidizes non-metals such as carbon (as bituminous coal) and sulfur. The Scrantons also experimented with anthracite to make steel, rather than charcoal or bituminous coal. Gas works would typically use oily bituminous coals as feedstock. The usual coal deposits of the area of bituminous or semi-bituminous coal.