metamorphic
Coal (Anthracite)
Anthracite (Carbon-based organic sedimentary/metamorphic rock)
Hardness: 2.5–3.0 (Mohs scale); Color: Black to dark steel-gray; Luster: Sub-metallic to vitreous; Crystal Structure: Amorphous; Cleavage: Conchoidal fracture; Specific gravity: 1.3–1.4
- Hardness
- 2
- Color
- Black to dark steel-gray
- Luster
- Sub-metallic to vitreous
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Physical properties
Hardness: 2.5–3.0 (Mohs scale); Color: Black to dark steel-gray; Luster: Sub-metallic to vitreous; Crystal Structure: Amorphous; Cleavage: Conchoidal fracture; Specific gravity: 1.3–1.4
Formation & geological history
Formed through the accumulation of plant debris in swamps (peat), followed by burial and extreme heat/pressure (metamorphism) over millions of years, typically during the Carboniferous period.
Uses & applications
Used primarily as a domestic fuel for heating and historically for locomotive power. It is also used in water filtration systems and as a component in the manufacture of steel.
Geological facts
Anthracite is the highest 'rank' of coal, containing the highest percentage of carbon and the fewest impurities. It burns with a short, blue, smokeless flame.
Field identification & locations
Identify in the field by its deep black color, high luster compared to other coals, and its tendency to not leave a black residue on fingers as easily as bituminous coal. Often found in folded mountain belts.
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