sedimentary
Coal
Bituminous or sub-bituminous coal (carbonaceous rock)
Hardness: 2.5-3 on the Mohs scale, Color: Black to dark brown, Luster: Dull to sub-vitreous, Crystal structure: Amorphous, Specific Gravity: 1.1-1.5
- Hardness
- 2
Identified More sedimentary →
Explore Coal in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 2.5-3 on the Mohs scale, Color: Black to dark brown, Luster: Dull to sub-vitreous, Crystal structure: Amorphous, Specific Gravity: 1.1-1.5
Formation & geological history
Formed from compressed plant remains in ancient wetland forests (swamps/peat bogs) over millions of years (primarily Carboniferous and Permian periods).
Uses & applications
Historically used as a primary fossil fuel for electricity generation, heating, and steel production.
Geological facts
Coal deposits record major climate and botanical shifts in Earth's history, preserving fossilized remains of ancient ferns, giant club mosses, and horsetails.
Field identification & locations
Lightweight relative to typical rocks, black and sooty to the touch, burns readily. Found in sedimentary basins worldwide.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary