sedimentary

Anthracite Coal

Anthracite (Carbon rank grade)

Hardness: 2.7-3.0 Mohs. Color: Deep black to dark iron-gray with iridescence. Luster: Sub-metallic to vitreous (glassy). Fracture: Conchoidal. Specific Gravity: 1.3-1.8.

Hardness: 2
Color: Deep black to dark iron-gray with iridescence
Luster: Sub-metallic to vitreous (glassy)

Identified July 27, 2026More sedimentary →

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Physical properties

Hardness: 2.7-3.0 Mohs. Color: Deep black to dark iron-gray with iridescence. Luster: Sub-metallic to vitreous (glassy). Fracture: Conchoidal. Specific Gravity: 1.3-1.8.

Formation & geological history

Formed through metamorphic alteration of peat and softer coals (bituminous) under intense heat and pressure over millions of years, primarily during the Carboniferous period.

Uses & applications

Historically used as a clean-burning fuel for heating and industrial processes. Currently sought by rock collectors for its mirror-like metallic luster and shiny conchoidal fractures.

Geological facts

Anthracite is the highest grade of coal, containing 86% to 97% carbon content. It burns with a short, blue, smokeless flame compared to lower-grade bituminous coal.

Field identification & locations

Identified by its jet-black color, vitreous to metallic sheen, surprisingly low density compared to metallic minerals, and clean hand-feel compared to sootier coals. Commonly found in Pennsylvania, USA.