sedimentary

Likely bituminous coal

Coal, predominantly carbon-rich organic matter with variable maceral and mineral content

AI-generated identification · may be incorrect

Black to dark brown, uneven and somewhat lustrous surface; coal has no fixed crystal structure or cleavage. Hardness is typically about 1–3 Mohs; the photo alone cannot confirm coal or its grade.

Identified September 25, 2026More sedimentary →

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Physical properties

Black to dark brown, uneven and somewhat lustrous surface; coal has no fixed crystal structure or cleavage. Hardness is typically about 1–3 Mohs; the photo alone cannot confirm coal or its grade.

Formation & geological history

Forms when buried plant material is compacted and altered by heat over millions of years, commonly in ancient swamp deposits; age varies by basin.

Uses & applications

Used as fuel and in steelmaking (especially suitable bituminous grades); attractive pieces may be kept as geological specimens.

Geological facts

Coal is an organic sedimentary rock, rather than a mineral, and its properties vary greatly with rank and impurities.

Field identification & locations

The dark color, layered-looking fracture, and subdued sheen are consistent with coal, but identification is uncertain from the image; a fresh streak and low density can help distinguish it from other dark rocks.