metamorphic
Anthracite Coal
Anthracite (Carbon-based sedimentary-derived metamorphic rock)
Hardness: 2.5–3 on Mohs scale; Color: Black to steel gray; Luster: Sub-metallic, vitreous to brilliant; Crystal Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific Gravity: 1.3–1.4
- Hardness
- 2
- Color
- Black to steel gray
- Luster
- Sub-metallic, vitreous to brilliant
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Physical properties
Hardness: 2.5–3 on Mohs scale; Color: Black to steel gray; Luster: Sub-metallic, vitreous to brilliant; Crystal Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific Gravity: 1.3–1.4
Formation & geological history
Formed through the low-grade metamorphism of bituminous coal under intense pressure and heat. This process (coalification) typically occurs in fold mountain belts and can date back to the Carboniferous period (300-360 million years ago).
Uses & applications
Primarily used as a high-quality fuel for domestic and industrial heating due to its high carbon content and low impurities. It is also used in water filtration systems and occasionally carved for decorative ornaments or jewelry (mourning jewelry).
Geological facts
Anthracite is the highest grade of coal, containing 86% to 98% carbon. It burns with a blue, smokeless flame and is the cleanest-burning coal variety. Famous deposits are found in the Appalachian Mountains of Pennsylvania.
Field identification & locations
Identify by its high luster (very shiny compared to other coal), lack of soot when handled, and the way it breaks into smooth, curved surfaces (conchoidal fracture). It is much harder and heavier than 'soft' bituminous coal.
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