metamorphic
Anthracite Coal
Anthracite (Carbon-based metamorphic rock, 86-97% C)
Hardness: 2.5-3.0 (Mohs scale); Color: Jet black to iron black; Luster: Submetallic, brilliant, or vitreous; Crystal Structure: Amorphous/Organic; Cleavage: Conchoidal fracture (no true cleavage); Specific Gravity: 1.3-1.8.
- Hardness
- 2
- Color
- Jet black to iron black
- Luster
- Submetallic, brilliant, or vitreous
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Physical properties
Hardness: 2.5-3.0 (Mohs scale); Color: Jet black to iron black; Luster: Submetallic, brilliant, or vitreous; Crystal Structure: Amorphous/Organic; Cleavage: Conchoidal fracture (no true cleavage); Specific Gravity: 1.3-1.8.
Formation & geological history
Formed through the regional metamorphism of bituminous coal in orogenic belts. It involves intense pressure and high temperatures that drive off volatiles like water and methane, concentrating carbon. It is the highest grade of coal.
Uses & applications
Historically used as a high-quality residential and industrial fuel due to its low sulfur and high energy density. Today, it is used in water filtration, metallurgy as a reducing agent, and occasionally for carvings or jewelry (jet-like).
Geological facts
Anthracite burns with a clean blue flame and produces very little smoke compared to other coal types. It represents only about 1% of global coal reserves. Unlike other coals, it is relatively clean to the touch and won't soil fingers easily.
Field identification & locations
Identify in the field by its high luster, deep black color, and conchoidal (shell-like) fracture. It is much harder and denser than bituminous coal. Found primarily in the Appalachian mountains of Pennsylvania, USA, as well as parts of South Wales and China.
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