metamorphic
Anthracite Coal
Anthracite (high-rank coal / Carbon)
Hardness: 2.5-3 (Mohs scale); Color: Black to steel gray with occasional iridescent colors; Luster: Sub-metallic to vitreous (glassy); Crystal structure: Amorphous/None; Cleavage: None (conchoidal fracture); Specific gravity: 1.3-1.7
- Hardness
- 2
- Color
- Black to steel gray with occasional iridescent colors
- Luster
- Sub-metallic to vitreous (glassy)
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Physical properties
Hardness: 2.5-3 (Mohs scale); Color: Black to steel gray with occasional iridescent colors; Luster: Sub-metallic to vitreous (glassy); Crystal structure: Amorphous/None; Cleavage: None (conchoidal fracture); Specific gravity: 1.3-1.7
Formation & geological history
Formed through the regional metamorphism of lower-grade coal (bituminous) under intense heat and pressure over millions of years, typically in areas of mountain building (orogeny). Most anthracite dates back between 300 to 360 million years ago.
Uses & applications
Primarily used as a residential and industrial fuel due to its high carbon content and low impurity levels. Since it burns cleanly and hot, it is used in metallurgy, water filtration, and occasionally as a base for fossil jewelry/carvings.
Geological facts
Anthracite is the highest rank of coal and has the highest carbon content (86%-98%). It accounts for only about 1% of the world's coal reserves. The largest deposits are in northeastern Pennsylvania, USA.
Field identification & locations
Identify by its light weight compared to its size, deep black color, and glassy luster that doesn't rub off on hands like lower-grade coal. Look for conchoidal (shell-like) fractures. Common in folded mountain regions and near coal mining districts.
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