metamorphic
Anthracite Coal
Anthracite (Carbon-rich metamorphic rock)
Hardness: 2.5–3.0 (Mohs scale); Color: Black or deep steel gray; Luster: Sub-metallic to vitreous (glassy); Structure: Amorphous/microcrystalline; Cleavage: Conchoidal fracture; Specific gravity: 1.3–1.8
- Hardness
- 2
- Color
- Black or deep steel gray
- Luster
- Sub-metallic to vitreous (glassy)
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Physical properties
Hardness: 2.5–3.0 (Mohs scale); Color: Black or deep steel gray; Luster: Sub-metallic to vitreous (glassy); Structure: Amorphous/microcrystalline; Cleavage: Conchoidal fracture; Specific gravity: 1.3–1.8
Formation & geological history
Formed through the regional metamorphism of bituminous coal in folded mountain belts. It is the highest rank of coal, having undergone the most intense pressure and heat over millions of years, typically dating to the Carboniferous period.
Uses & applications
Historically used as a high-quality domestic fuel and for steam generation due to its high energy density and low smoke. Currently used in metallurgy, water filtration systems, and as a material for carvings.
Geological facts
Anthracite contains the highest percentage of fixed carbon (86% to 97%) and the lowest level of impurities among all coal types. It is often referred to as 'hard coal' or 'black diamond.'
Field identification & locations
Identify in the field by its high luster, lightness (low density), and the fact that it does not soil fingers when handled (unlike softer coals). Common in highly deformed geological areas like the Appalachian Mountains in Pennsylvania.
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