Which form of coal is the hardest?

• A. Lignite
• B. Bituminous
• C. Anthracite
• D. Peat

Answer: (C)

Hardness rises as coal forms through increasing heat and pressure, which drives off moisture and volatiles and boosts carbon content. Anthracite sits at the top of this progression, so it is the hardest. It has the highest carbon content and the least moisture and volatile matter, resulting in a dense, compact, and very tough material that resists breaking. This high density and carbon content also give it a high energy value and a clean, bright burn. In contrast, peat isn’t yet coal, lignite is soft and crumbly with more moisture, and bituminous coal, while energy-rich, is still less hard than anthracite.