metamorphic
Anthracite Coal
Anthracite (Carbon based)
Hardness: 2.5–3.0 on Mohs scale; Color: Black or dark iron-grey; Luster: Submetallic, glass-like (vitreous); Structure: Amorphous/Non-crystalline; Fracture: Conchoidal; Specific Gravity: 1.3–1.4
- Hardness
- 2
- Color
- Black or dark iron-grey
- Luster
- Submetallic, glass-like (vitreous)
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Physical properties
Hardness: 2.5–3.0 on Mohs scale; Color: Black or dark iron-grey; Luster: Submetallic, glass-like (vitreous); Structure: Amorphous/Non-crystalline; Fracture: Conchoidal; Specific Gravity: 1.3–1.4
Formation & geological history
Formed through the regional metamorphism of bituminous coal in sedimentary basins. Most deposits date back to the Carboniferous period (300-360 million years ago), where intense heat and pressure from tectonic activity pushed out impurities and moisture.
Uses & applications
Primary use is for domestic and industrial heating due to high energy density and low smoke. Historically used in metallurgy and water filtration. Occasionally used by hobbyists for carving and folk art jewelry (jet-like).
Geological facts
Anthracite is the highest rank of coal, containing 86%–97% carbon. Unlike lower grades of coal, it burns with a short, blue, smokeless flame. It is the bridge between sedimentary coal and graphite.
Field identification & locations
Identify by its 'clean' feel—unlike softer coal, it rarely leaves black soot on the hands. It is much harder and more lustrous than bituminous coal. Common in the Appalachian Mountains (Pennsylvania, USA), Wales, and China. In the field, look for brittle, shiny black rocks with shell-like curved fractures.
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