Quick Facts
Formation & Origin
Jet is fossilized wood - specifically, the remains of Araucaria-type coniferous trees that fell into anoxic (oxygen-free) swamp or marine environments during the Jurassic period, roughly 180 million years ago. Under pressure and in the absence of oxygen, the wood underwent a process similar to coal formation but retained more of its original cellular structure.
Jet from Whitby, England, formed from trees that fell into a Jurassic sea and were buried in marine shale. This distinguishes it from 'hard jet' that formed in freshwater environments - the marine Whitby jet is denser and takes a better polish. Whitby has been the world's premier jet source since the Bronze Age.
Jet is extremely lightweight (SG 1.30 - it barely sinks in water), warm to the touch, and generates static electricity when rubbed - properties it shares with amber, another organic gem. Despite being millions of years old, jet retains enough volatile compounds to burn with a smoky flame, which was used historically as an identification test.
Identification Guide
Jet is identified by its intense black color, very low density (feels surprisingly light), warmth to the touch, and ability to generate static charge when rubbed on fabric. The streak is dark brown, not black.
Distinguish from obsidian (much denser, glassy fracture, cold to touch), black onyx (much denser, harder), black tourmaline (crystal faces, much denser), and glass (cold, denser). Jet's extreme lightness is its most practical diagnostic - if a black material feels unexpectedly light, it's likely jet or plastic.
Spotting Fakes
Bakelite, vulcanite (vulcanized rubber), and other black plastics are the most common jet substitutes. The hot needle test helps: jet smells of burning coal, while plastic smells acrid. Jet also generates static electricity when rubbed, which most plastics don't. French jet (black glass) is cold and heavy compared to genuine jet. The weight test is fastest - genuine jet is remarkably lightweight for its appearance. 'Bog oak' (naturally darkened wood) is sometimes sold as jet but is softer and shows visible wood grain.
Cultural & Metaphysical Traditions
Presented as cultural traditions, not scientific evidence
Jet has been used since the Neolithic period - jet beads have been found in British burial sites dating to 4,000 years ago. The Romans believed jet could detect illness and evil. But jet's most famous cultural role was in Victorian mourning jewelry. After Prince Albert's death in 1861, Queen Victoria wore Whitby jet exclusively, creating a massive demand. Whitby's jet industry employed over 1,500 workers at its peak. Jet became synonymous with mourning and grief across the English-speaking world.
Where It's Found
World's most famous jet, Victorian-era production
Important European source, fine quality
Traditional carving material
Some material available
Price Guide
Good to Know
Scratch test: At hardness 3, Jet can be scratched with a copper coin. Handle gently and keep away from harder stones in your collection.
Sources: Found in 4 notable locations worldwide, from England to United States.
Heft test: With a specific gravity of 1.30, Jet feels lighter than most minerals. This lightness can help identify it.
Related Minerals
Another organic gem, fossilized resin vs fossilized wood
Similar black color, completely different origin (volcanic)
Similar appearance, mineral vs organic
Related fossilized plant material, less compact