metamorphic
Anthracite Coal
Anthracite (high-rank coal)
Hardness: 2.5-3.0 Mohs; Color: Jet black to iron-black; Luster: Submetallic, vitreous (glassy); Structure: Amorphous/conchoidal fracture; SG: 1.3-1.4
- Hardness
- 2
- Color
- Jet black to iron-black
- Luster
- Submetallic, vitreous (glassy)
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Physical properties
Hardness: 2.5-3.0 Mohs; Color: Jet black to iron-black; Luster: Submetallic, vitreous (glassy); Structure: Amorphous/conchoidal fracture; SG: 1.3-1.4
Formation & geological history
Formed through the low-grade metamorphism of bituminous coal under intense heat and pressure over millions of years, typically in fold belts of mountain building events. Contains 86% to 97% carbon.
Uses & applications
Primarily used as a source of energy for space heating and in the steel industry. High-quality specimens are used for ornamental carvings and jewelry, known as 'jet' in some decorative contexts.
Geological facts
It is the highest rank of coal and burns with a clean, blue flame with very little smoke. It is often referred to as 'hard coal' because it does not soil fingers when handled, unlike lower ranks of coal.
Field identification & locations
Identify by its light weight, glassy black appearance, and tendency to break with smooth, curved surfaces (conchoidal fracture). Commonly found in the Appalachian region of Pennsylvania, USA.
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