Bituminous Coal
Carbon var. Coal / Organic Sedimentary Rock · Organic Mineraloid / Energy Mineral
Crystal System
Amorphous (Non-crystalline)
Mineral Group
Organic Carbon Compounds / Sedimentary Rock
Chemical Formula
C (with variable amounts of H, O, N, S, and moisture)
Formation Process
Sedimentary accumulation and burial of plant debris in swampy environments, followed by lithification, compaction, and increasing temperature and pressure over millions of years (diagenesis and catagenesis)
About This Crystal
An opaque, black to dark brown rock fragment with a dull to sub-vitreous luster, showing characteristic blocky or irregular fracture patterns, porous texture, and fine surface cracking.
Physical Characteristics
Color is deep black with a dark brown to black streak, amorphous habit with no cleavage, uneven to conchoidal fracture, specific gravity around 1.3 to 1.4, brittle tenacity, and non-magnetic.
Optical Properties
Opaque with no refractive index, birefringence, or pleochroism; light is completely absorbed rather than transmitted or refracted.
Hardness & Durability
Origin Region
Worldwide, notably found in North America (Appalachia), China, Russia, Australia, and Europe in sedimentary coal basins
Hardness & Durability
Mohs hardness of 1.5 to 2.5, low toughness, highly combustible, fragile and unsuitable for jewelry wear.
Care & Maintenance
Store in a dry environment away from open flames, high heat sources, and strong oxidizing agents to prevent spontaneous combustion or degradation.
Rarity & Value
Common, widely utilized as an industrial and energy resource with very low specimen value except for specialized varieties like jet.
Special Characteristics
Highly combustible, exhibits volatile matter release upon heating, and retains microscopic plant cell structures visible under analysis.
Lore & History
Historically used as a primary fossil fuel driving the Industrial Revolution, culturally associated with grounding and transformation in alternative belief systems, though scientifically recognized as a fossilized organic sedimentary rock.