metamorphic
Anthracite Coal
Anthracite (Carbon-based sedimentary rock typically classified as metamorphic)
Hardness: 2.5-3 (Mohs scale), Color: Jet black to dark gray, Luster: Sub-metallic to vitreous (glassy), Structure: Amorphous (non-crystalline), Cleavage: Conchoidal fracture, Specific Gravity: 1.3-1.8
- Hardness
- 2
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Physical properties
Hardness: 2.5-3 (Mohs scale), Color: Jet black to dark gray, Luster: Sub-metallic to vitreous (glassy), Structure: Amorphous (non-crystalline), Cleavage: Conchoidal fracture, Specific Gravity: 1.3-1.8
Formation & geological history
Formed through the regional metamorphism of bituminous coal. It undergoes intense heat and pressure over millions of years, typically in folded mountain belts like the Appalachians. It dates primarily from the Carboniferous Period.
Uses & applications
Primarily used for domestic heating due to high energy density and low smoke. Historically used in metallurgy and water filtration. Occasionally used in jewelry or as a carbon source for manufacturing.
Geological facts
Anthracite has the highest carbon content of all coal types (86% to 98%) and contains the fewest impurities. It is the oldest and hardest of the coal varieties and burns with a short blue flame without smoke.
Field identification & locations
Identify by its light weight relative to its dark metallic appearance, shell-like (conchoidal) fractures, and the fact that it does not leave a black smudge on fingers like standard coal. Found in Pennsylvania (USA), Wales (UK), and Vietnam.
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