sedimentary
Anthracite Coal
Anthracite (Carbon-rich metamorphic sedimentary rock)
Hardness: 2.5-3 (Mohs scale); Color: Jet black to dark grey; Luster: Sub-metallic to vitreous (glassy); Crystal structure: Amorphous; Cleavage: None (conchoidal fracture); Specific gravity: 1.3-1.7
- Hardness
- 2
- Color
- Jet black to dark grey
- Luster
- Sub-metallic to vitreous (glassy)
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Physical properties
Hardness: 2.5-3 (Mohs scale); Color: Jet black to dark grey; Luster: Sub-metallic to vitreous (glassy); Crystal structure: Amorphous; Cleavage: None (conchoidal fracture); Specific gravity: 1.3-1.7
Formation & geological history
Formed through the regional metamorphism of bituminous coal over millions of years. It occurs in areas of intense folding and faulting where high pressure and temperature drive out volatile matter, leaving high carbon content.
Uses & applications
Primarily used for heating residential and commercial spaces, as a fuel in specialized industrial processes, and sometimes in water filtration systems. Highly polished pieces are occasionally used in jewelry or as decorative carvings.
Geological facts
Anthracite is the highest grade of coal, containing 86% to 97% carbon. Unlike other coals, it burns with a clean blue flame and produces very little smoke or soot. It is sometimes referred to as 'hard coal' or 'black diamond.'
Field identification & locations
Identified in the field by its dark black color, relative hardness compared to other coals, and its shiny, almost metallic luster. It is cleaner to handle than bituminous coal as it does not leave as much black residue on skin. Found predominantly in the Appalachian region of Pennsylvania, USA.
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