When the figure is not level people cannot know what is meant by width, depth, or height without being told (or without labels), although length is generally still assumed to mean the direction in which the figure is longest..
The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.oal is primarily used as a solid fuel to produce electricity and heat through combustion. World coal consumption was about 7.25 billion tonnes in 2010 (7.99 billion short tons) and is expected to increase 48% to 9.05 billion tonnes (9.98 billion short tons) by 2030.
Anthracite coal is a form of coal that is almost made entirely of carbon. Anthracite coal is much harder than other forms of coal such as bituminous, and is usually found in areas surrounding mountains or deep valleys.Anthracite burns much cleaner than other forms of coal due to its low pollutant content.nthracite coal is the cleanest form of coal as it produces very little pollution and does not stain skin when touched, unlike most forms of coal. While anthracite coal is more difficult to burn, it produces more heat than other types of coal.