metamorphic
Anthracite Coal
Anthracite
Hardness: 2.5–3.0 on Mohs scale; Color: Black to steel-gray; Luster: Submetallic, vitreous; Crystal Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 1.3–1.8
- Hardness
- 2
- Color
- Black to steel-gray
- Luster
- Submetallic, vitreous
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Physical properties
Hardness: 2.5–3.0 on Mohs scale; Color: Black to steel-gray; Luster: Submetallic, vitreous; Crystal Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 1.3–1.8
Formation & geological history
Formed through the low-grade metamorphism of bituminous coal under intense pressure and heat within the earth's crust, typically during mountain-building events (orogenies). Most specimens date back to the Carboniferous period, approx. 300 to 360 million years ago.
Uses & applications
Historically used as a high-grade fuel for domestic heating and industrial smelting due to high carbon content and low impurities; also used for water filtration and as a decorative stone for carving.
Geological facts
Anthracite contains the highest percentage of fixed carbon (86% to 98%) of all coal types and burns with a short, blue flame and very little smoke. It is often referred to as 'hard coal' compared to the 'soft' bituminous coal.
Field identification & locations
Identify in the field by its high luster, cleanliness to the touch (unlike sootier coals), and conchoidal fracture. Commonly found in folded mountain belts like the Appalachian Mountains in Pennsylvania, USA, and parts of Wales and China.
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