metamorphic
Anthracite Coal
Anthracite (Carbon-rich Sedimentary-to-Metamorphic Rock)
Hardness: 2-2.5 on Mohs scale; Color: Black to deep iron-gray; Luster: Sub-metallic to vitreous (glassy); Crystal Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific Gravity: 1.3 to 1.8.
- Hardness
- 2-2
- Color
- Black to deep iron-gray
- Luster
- Sub-metallic to vitreous (glassy)
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Physical properties
Hardness: 2-2.5 on Mohs scale; Color: Black to deep iron-gray; Luster: Sub-metallic to vitreous (glassy); Crystal Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific Gravity: 1.3 to 1.8.
Formation & geological history
Formed through the prograde metamorphism of bituminous coal. Intense pressure and heat over millions of years (often Carboniferous period, approx. 300-360 million years old) drive off moisture and volatile matter, leaving a high carbon content.
Uses & applications
Primarily used as a high-grade fuel for residential and industrial heating. It's also used in water filtration systems and, occasionally, carved into folk art or jewelry (jet-like items).
Geological facts
Anthracite is the highest rank of coal, containing 86%-98% carbon. Unlike softer coals, it burns with a short, blue, smokeless flame. It is often referred to as 'hard coal' or 'black diamond.'
Field identification & locations
Identify in the field by its high sheen, light weight relative to stone, and 'clean' feel (it does not soil fingers like softer coal). Commonly found in the Appalachian Mountains of Pennsylvania, USA, and parts of Wales and China.
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