sedimentary

Bituminous coal (likely)

Coal, primarily carbon with macerals and variable mineral matter; commonly represented by approximate composition C-rich organic material

AI-generated identification · may be incorrect

Black, opaque, vitreous to dull luster with irregular blocky/fractured surfaces; Mohs hardness about 2–3, low density, and no consistent crystal structure. The appearance may also fit anthracite, but the specimen is too weathered for confident rank identification.

Identified September 4, 2026More sedimentary →

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At a glance

Common name: Bituminous coal (likely)
Scientific name: Coal, primarily carbon with macerals and variable mineral matter; commonly represented by approximate composition C-rich organic material
Category: sedimentary
Identified: September 4, 2026
Method: Standard

AI Estimated Value

Typically $1–$15 for a common rough hand specimen; unusual polished, fossil-rich, or historically documented pieces may bring $20–$100+.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Formed from compacted and thermally altered plant material in ancient swamp deposits, commonly during the Carboniferous (about 359–299 million years ago), though coal occurs in many younger basins.

Uses & applications

Used chiefly as fuel and historically for coke and steelmaking; attractive polished coal can be collectible, but this rough piece has limited commercial value.

Geological facts

Coal may show plant bands, conchoidal or stepped fractures, and can soil hands; anthracite is harder, denser, and more strongly lustrous than bituminous coal.

Field identification & locations

Common in coal basins worldwide, including the Appalachian, Illinois, and Powder River regions. Confirm by low density, black streak, combustible behavior, and lack of glassy crystal structure; avoid testing unknown specimens by burning indoors.