metamorphic
Anthracite Coal
Anthracite (Carbon-rich metamorphic rock)
Hardness: 2.5-3.0; Color: Black to metallic grey; Luster: Sub-metallic to vitreous (glassy); Structure: Amorphous/microcrystalline; Fracture: Conchoidal; Specific Gravity: 1.3-1.8.
- Hardness
- 2
- Color
- Black to metallic grey
- Luster
- Sub-metallic to vitreous (glassy)
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Physical properties
Hardness: 2.5-3.0; Color: Black to metallic grey; Luster: Sub-metallic to vitreous (glassy); Structure: Amorphous/microcrystalline; Fracture: Conchoidal; Specific Gravity: 1.3-1.8.
Formation & geological history
Formed through the low-grade metamorphism of bituminous coal under intense heat and pressure over millions of years. Most deposits formed during the Carboniferous period (approx. 300-360 million years ago) in swampy environments.
Uses & applications
Primarily used as a residential and industrial fuel due to its high energy density and low smoke. Historically used in metallurgy and currently used in water filtration systems.
Geological facts
Anthracite is the highest grade of coal, containing between 86% and 97% carbon. It is often referred to as 'hard coal' and burns with a short blue flame and very little smoke compared to other coal types.
Field identification & locations
Identify by its high luster (shininess), clean feel (does not leave soot on hands like lower-grade coal), and conchoidal fracture patterns. Commonly found in Pennsylvania, USA, and parts of China and Russia.
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