Anthracite Coal

Hardness: 2.5–3.0 on Mohs scale; Color: Black to steel-gray; Luster: Sub-metallic to vitreous (glassy); Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific gravity: 1.3–1.7.

Formed from the remains of prehistoric plants that were buried and subjected to high heat and pressure over millions of years (primarily Carboniferous period, approx. 300-360 million years ago). It is the highest grade of coal, having undergone the most metamorphism.

Primarily used for domestic heating and industrial processes requiring high-energy smokeless fuel. Historically used in metallurgy. Occasionally used for carving and folk art jewelry (similar to jet).

Anthracite contains the highest percentage of carbon (86%-97%) of all coal types. It burns with a short blue flame and produces very little smoke or soot compared to bituminous coal. It is often referred to as 'hard coal'.

Look for a jet-black color, high luster, and a smooth, curved (conchoidal) fracture pattern similar to glass. It leaves a black streak on a porcelain plate and is notably lighter in weight than typical silicate rocks. Commonly found in the Appalachian mountains of Pennsylvania, USA, and parts of South Wales.