sedimentary
Anthracite Coal
Anthracite (Metamorphosed Coal)
Hardness: 2.5 - 3.0 on Mohs scale; Color: Black to dark steel-gray; Luster: Sub-metallic to brilliant/vitreous; Crystal structure: Amorphous; Cleavage: None (conchoidal fracture); Specific gravity: 1.3 - 1.8
- Hardness
- 2
- Color
- Black to dark steel-gray
- Luster
- Sub-metallic to brilliant/vitreous
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Physical properties
Hardness: 2.5 - 3.0 on Mohs scale; Color: Black to dark steel-gray; Luster: Sub-metallic to brilliant/vitreous; Crystal structure: Amorphous; Cleavage: None (conchoidal fracture); Specific gravity: 1.3 - 1.8
Formation & geological history
Formed through the deep burial and low-grade metamorphism of peat and lower-rank coals over millions of years (often Carboniferous period). It requires high pressure and temperature to expel volatile matter, leaving a high carbon content.
Uses & applications
Primary use as a high-grade fuel for domestic heating and industrial power generation. Historically used in metallurgy and water filtration media.
Geological facts
Anthracite is the highest rank of coal, containing 86% to 97% carbon. It burns with a short, blue, smokeless flame and is often referred to as 'hard coal' to distinguish it from softer bituminous coal.
Field identification & locations
Identify in the field by its high luster, clean touch (it does not leave as much soot on fingers as bituminous coal), and conchoidal (shell-like) fracture. Found in folded mountain belts like the Appalachian Mountains in Pennsylvania.
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