metamorphic
Anthracite Coal
High-rank coal (primarily Carbon, C)
Hardness: 2.5-3.0; Color: Jet black to dark grey; Luster: Sub-metallic to vitreous (glassy); Structure: Amorphous/Non-crystalline; Cleavage: Conchoidal fracture; Specific Gravity: 1.3-1.8
- Hardness
- 2
- Color
- Jet black to dark grey
- Luster
- Sub-metallic to vitreous (glassy)
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Physical properties
Hardness: 2.5-3.0; Color: Jet black to dark grey; Luster: Sub-metallic to vitreous (glassy); Structure: Amorphous/Non-crystalline; Cleavage: Conchoidal fracture; Specific Gravity: 1.3-1.8
Formation & geological history
Formed through the regional metamorphism of bituminous coal in sedimentary basins. It involves high heat and pressure over millions of years (often Carboniferous period, ~300-360 Ma) which drives off volatile matter and moisture.
Uses & applications
Primarily used for heating (domestic fuel), industrial processes requiring high carbon content, and sometimes carved for folk art or jewelry (jet-like).
Geological facts
Anthracite is the highest rank of coal, containing between 86% and 97% carbon. It burns with a short, blue, smokeless flame and is the cleanest burning form of coal.
Field identification & locations
Identify by its high luster, clean feel (does not soil fingers as much as softer coal), and tendency to break in curved, shell-like patterns. Common in the Appalachian region of Pennsylvania.
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