Jet
Lignite var. Jet · Organic Gem
Crystal System
Amorphous (Non-crystalline)
Mineral Group
Organic Mineraloid
Chemical Formula
C (Carbon-rich amorphous organic material derived from degraded wood)
Formation Process
Sedimentary organic fossilization of wood from specific trees (like auraucarian trees) under high pressure in marine shales and mudstones over millions of years
About This Crystal
Deep black to brownish-black organic gemstone with a smooth, velvety texture when polished. Opaque with a sub-vitreous to resinous or waxy luster, showing typical conchoidal fracture surfaces and sometimes natural wood grain structures.
Physical Characteristics
Color is deep jet black or brownish-black; streak is brownish-black; cleavage is absent; fracture is distinctly conchoidal; specific gravity is low (1.30 to 1.34); tenacity is somewhat brittle but tough enough to be carved; non-magnetic and non-fluorescent.
Optical Properties
Singly refractive (amorphous), isotropic, refractive index is approximately 1.66, no pleochroism, exhibits a rich velvet-like luster when polished rather than the bright reflections of stones like obsidian.
Hardness & Durability
Origin Region
Yorkshire (Whitay, England), Spain, France, United States (Utah, Colorado)
Hardness & Durability
Mohs hardness is 2.5 to 4.0; low durability and scratches easily; sensitive to heat, alcohol, and prolonged chemical exposure; requires gentle handling and care when worn as jewelry.
Care & Maintenance
Clean only with a soft damp cloth and mild soap; avoid ultrasonic cleaners, steam cleaners, harsh chemicals, alcohol, and prolonged direct sunlight; store separately in a soft pouch to prevent scratching from harder gemstones.
Rarity & Value
Uncommon to Rare for high-grade uniform material like Whitby jet; value is determined by deep black color, absence of fractures, uniformity, and historical provenance; treated plastics or black glass (French jet) are common imitations.
Special Characteristics
Becomes electrically charged when rubbed (triboelectric effect, similar to amber); light in weight compared to mineral gemstones due to its low density and organic carbon-based composition.
Lore & History
Highly significant in Victorian mourning jewelry following the death of Prince Albert; used since the Neolithic era for amulets and beads; traditionally believed to offer protection from negative energies and grief, associated with the root chakra in modern crystal lore.