Coal

Physical Properties

Hardness: 0.5-2.5 on Mohs scale; Color: black to brownish-black; Luster: dull to sub-metallic/glassy; Structure: amorphous or microcrystalline; Cleavage: none (cleat/fracture)

Formation & Geological History

Formed from the accumulation and burial of plant remains in swampy environments over millions of years, subjected to heat and pressure (coalification).

Uses & Applications

Primary source of fuel for electricity generation, industrial heat, and production of coke for steel manufacturing.

Geological Facts

Coal is the most abundant fossil fuel on Earth; it contains stored energy from plants that lived hundreds of millions of years ago in swampy forests.

Field Identification & Locations

Identified by its lightweight feel, black streak, and tendency to smudge hands. Often found in layered beds or seams within sedimentary basins.

Identified on: 5/15/2026

Mode: Standard