sedimentary

Likely anthracite coal fragments

Anthracite; predominantly carbon (C), with minor mineral ash

AI-generated identification · may be incorrect

Black to steel-gray, vitreous to submetallic luster, brittle with conchoidal-to uneven fracture and faint layering; Mohs hardness about 2.5–3, specific gravity roughly 1.4–1.8. The shiny surfaces and banded texture are consistent with coal, though the image alone cannot exclude graphite-rich rock or industrial slag.

Identified August 31, 2026More sedimentary →

Explore Likely anthracite coal fragments in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Anthracite forms when bituminous coal is deeply buried and subjected to elevated heat and pressure during regional metamorphism, commonly during mountain-building events; its exact geological age depends on the coal basin. It is not technically an igneous, sedimentary, or metamorphic rock in many classifications, but coal originates as sedimentary organic matter and anthracite is metamorphosed coal.

Uses & applications

Used mainly as a high-carbon fuel, reducing agent, and filtration media; attractive polished pieces may be collected but are rarely used as gemstones.

Geological facts

Anthracite is the highest-rank coal, with typically over 86% fixed carbon and relatively low volatile matter. It burns hotter and cleaner than lower-rank coal, but the pictured pieces could also be coal waste or slag.

Field identification & locations

Identify by lightweight black fragments, bright resinous/metallic sheen, layered structure, and black streak; it commonly occurs in coalfields such as Pennsylvania, Wales, and northeastern China. A hardness, streak, density, and magnetic test would help distinguish it from slag or graphite.