Jet (jewellery material)

What is jet?

Jet, called gagat or jett in Norwegian, is a black organic material formed from fossil wood. It can be worked and polished into jewellery. It is not black glass or amber. Whitby in England is particularly associated with jet, but a Whitby origin should not be stated as certain without supporting evidence.

Confusions in older jewellery

Black glass, vulcanite and other materials have been used as imitations. French jet denotes black glass, not a distinct French variety of natural jet. Colour and a glossy surface alone are therefore insufficient for identification.

Gem-A demonstrates that different materials may resemble each other in shape and ornament. Consider workmanship, visible moulding features, joints and repairs as well. These observations provide clues rather than a conclusive material analysis.

Advice for buyers and collectors

Document the complete piece, reverse, clasp and damage before assessment. Do not use burning, a hot needle or scratching as a home test on a collectable. If the material is uncertain, obtain a specialist examination before selling it as natural jet or claiming a particular geographical origin.

Store the jewellery away from hard objects that could scratch its surface. Choose a cleaning method only after the material, glued joints and mounting have been established. Browse our jewellery category.

Sources

Whitby Museum, Gem-A on jet and simulants and Store norske leksikon on gagat.