metamorphic
Anthracite Coal
Anthracite
Hardness: 2.5-3 (Mohs). Color: Black to dark steel gray. Luster: Submetallic, vitreous, or brilliant. Crystal structure: Amorphous (non-crystalline). Cleavage: Conchoidal fracture. Specific gravity: 1.3-1.8.
- Hardness
- 2
- Color
- Black to dark steel gray
- Luster
- Submetallic, vitreous, or brilliant
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Physical properties
Hardness: 2.5-3 (Mohs). Color: Black to dark steel gray. Luster: Submetallic, vitreous, or brilliant. Crystal structure: Amorphous (non-crystalline). Cleavage: Conchoidal fracture. Specific gravity: 1.3-1.8.
Formation & geological history
Formed through the prograde metamorphism of bituminous coal at high temperatures and pressures. This geological process focuses carbon and removes volatiles. Most date to the Carboniferous period (300-360 million years ago).
Uses & applications
Primarily used as a high-grade fuel for domestic and industrial heating because it burns with a clean blue flame. Historically used in metallurgy; currently popular for carvings and as a collector specimen.
Geological facts
Anthracite has the highest carbon content (86%-97%) of all coal types. It is often referred to as 'hard coal' or 'black diamond.' Because it burns so cleanly, it was the preferred fuel for locomotives in the early 20th century.
Field identification & locations
Identify in the field by its high luster, lightness (low density), and the fact that it does not soil fingers like softer coals. Commonly found in the Appalachian Mountains of Pennsylvania, USA, and parts of Wales and China.
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