metamorphic
Anthracite Coal
Anthracite (Carbon-rich metamorphic rock)
Hardness: 2.0-2.5 on Mohs scale; Color: Black to dark steel gray; Luster: Submetallic, vitreous (shiny); Crystal Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 1.3-1.7.
- Hardness
- 2
- Color
- Black to dark steel gray
- Luster
- Submetallic, vitreous (shiny)
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Physical properties
Hardness: 2.0-2.5 on Mohs scale; Color: Black to dark steel gray; Luster: Submetallic, vitreous (shiny); Crystal Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 1.3-1.7.
Formation & geological history
Formed from the high-grade metamorphism of sedimentary bituminous coal under intense pressure and temperature within the Earth's crust. Most coal deposits formed during the Carboniferous period (approx. 300 to 360 million years ago) in swampy environments.
Uses & applications
Used primarily as a high-quality residential and industrial fuel due to its high carbon content and low impurities; also used in water filtration systems and as a source of carbon for various industrial processes.
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 shiny, black, glass-like appearance and its relative lightness compared to rocks of similar size. It will not leave a dark smudge on your fingers as easily as lower-grade coal. Commonly found in folded mountain belts like the Ridge-and-Valley Appalachians in Pennsylvania, USA.
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