metamorphic
Anthracite Coal
Anthracite (Carbon Content: 86%–98%)
Hardness: 2.5–3.0 Mohs; Color: Jet black to dark gray with a metallic or sub-metallic luster; Texture: Conchoidal fracture (glass-like break); Crystal Structure: Amorphous; Specific Gravity: 1.3–1.8.
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Physical properties
Hardness: 2.5–3.0 Mohs; Color: Jet black to dark gray with a metallic or sub-metallic luster; Texture: Conchoidal fracture (glass-like break); Crystal Structure: Amorphous; Specific Gravity: 1.3–1.8.
Formation & geological history
Formed through the regional metamorphism of bituminous coal. Intense heat and pressure over millions of years (primarily Carboniferous and Permian periods) drive off moisture and volatile matter, leaving high carbon density.
Uses & applications
Historically used as a high-grade fuel for domestic heating and metallurgy due to low smoke and high energy output. Today, it is used for water filtration, steel making, and occasionally in the carving of ornaments or 'jet' imitation jewelry.
Geological facts
Anthracite is the highest rank of coal. Unlike lower grades, it burns with a blue flame and produces very little soot. It is often referred to as 'hard coal' or 'black diamond' in older literature.
Field identification & locations
Identify by its high shine (luster), lack of soiling when handled compared to other coals, and its tendency to break in smooth, curved surfaces rather than blocks. Commonly found in folded mountain belts like the Appalachian Mountains in Pennsylvania, USA.
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