sedimentary
Coal (Anthracite / Bituminous)
Organic Sedimentary Rock (Carbon-based)
Hardness: 1.5 to 2.5 on Mohs scale; Color: Black to dark brownish-black; Luster: Sub-metallic to vitreous or dull; Structure: Amorphous/non-crystalline; Cleavage: None (conchoidal to uneven fracture); Specific Gravity: 1.1–1.5.
- Hardness
- 1
- Color
- Black to dark brownish-black
- Luster
- Sub-metallic to vitreous or dull
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Physical properties
Hardness: 1.5 to 2.5 on Mohs scale; Color: Black to dark brownish-black; Luster: Sub-metallic to vitreous or dull; Structure: Amorphous/non-crystalline; Cleavage: None (conchoidal to uneven fracture); Specific Gravity: 1.1–1.5.
Formation & geological history
Formed from compressed plant matter (peat) in ancient swamp environments under heat and pressure over tens to hundreds of millions of years. Commonly found in Carboniferous to Permian strata, such as in Pennsylvania and the broader Appalachian Basin.
Uses & applications
Historically and currently used primarily as fossil fuel for electricity generation, industrial heat, steel manufacturing (coking coal), and occasionally for carving or mineral collecting specimens.
Geological facts
Pennsylvania is famous for its extensive deposits of high-grade anthracite coal as well as bituminous coal. Coal is actually a fossilized sedimentary rock made almost entirely of carbonized organic material rather than inorganic minerals.
Field identification & locations
Identified by its low density (surprisingly light for its size), black streak, brittle fracture, and combustion capability. Highly consistent with specimens found across eastern Pennsylvania and New Jersey river/rail networks.
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