Whitby jet: what it is, and how to tell it from a fake

What Whitby jet actually is

Jet is fossilised wood. The tree it came from was a species related to the Chilean pine, the monkey puzzle, Araucaria araucana. It is Early Jurassic, of Toarcian age, and the published figures cluster around 181 to 183 million years, which is close enough to say around 180 million years old and leave the false precision alone.

Whitby Museum describes it as fossilised driftwood with a secondary impregnation of bitumen drawn from the host rocks, formed by a process known as jetonisation rather than ordinary petrification. That is why it behaves nothing like stone in the hand. It is roughly 75% carbon and 12% oxygen, and its hardness on the Mohs scale runs from 2.5 to 4.0: soft enough to carve and polish with hand tools, brittle enough to chip if you drop it.

Jet is not unique to Yorkshire. It occurs in Spain, Germany, Portugal, France and Turkey as well, though only the British, Spanish and Turkish industries survive. What is particular to this coast is the length of the story: jet has been worked in Britain since the Bronze Age, while the industry, the workshops, the mines and the shop fronts, is a 19th-century thing.

The Victorian boom, and the collapse

Commercial working in Whitby dates from the 1830s, given an early boost by the death of George IV in 1830. The transformation came later. Prince Albert died in 1861, Victoria went into mourning for over forty years until her own death in 1901, and jet, black, light and carvable, became the jewellery of mourning for a whole society that followed her lead.

At the peak, between 1860 and 1880, there were over 200 jet workshops in Whitby employing around 1,500 men, women and children, supplied by some 300 mines. For a town of this size that is an extraordinary concentration of one trade.

The collapse was as sharp. Spanish imports are documented from 1874, bringing in inferior material that degraded in wear, and public confidence went with it. The fashion passed at much the same time, and by the end of the century the industry had gone. There has been a smaller revival in recent years, on nothing like the old scale, and it is that revival you are looking at in the Church Street workshops today.

How to tell real jet from an imitation

This is the question the shops have least reason to answer plainly, so here it is. The two tests you can do standing in a shop are the useful ones.

It feels warm. Jet conducts heat poorly, so it takes on the temperature of your hand almost at once. Glass feels cold and stays cold for a moment. This single difference catches most of the black glass sold as jet.

It is surprisingly light. Pick up a jet bead next to a glass one of the same size and the weight tells you immediately which is which.

The streak test is the one everybody quotes: rubbed on unglazed porcelain, jet leaves a brown streak. Say plainly what that is worth, which is not much on its own, because bog oak, vulcanite and lignite all streak brown too. A brown streak rules out glass. It does not prove jet.

The burn test exists, and real jet smells of coal. It also destroys the piece. Nobody should do it to jewellery, and no reputable seller will let you.

The imitations worth knowing by name: French jet and Vauxhall glass, both black glass; vulcanite, also called ebonite, which fades with age from black towards a dull brown-green; bog oak; and anthracite. Where to buy from the established jet shops and the working jetworks is in our Whitby shopping guide.

Where to see it

Whitby Museum, in Pannett Park, founded in 1823, is the place. It holds over 500 Victorian jet pieces, one of the best collections of Victorian jet in the world, including two jet chess tables, one of them designed by John Sherwood and begun in 1895. It is a proper old-fashioned museum, and the jet sits alongside the fossils that came out of the same cliffs.

The Museum of Whitby Jet and the working jetworks on Church Street are described on our shopping page, where you can also watch pieces being cut. Opening times and admission change from season to season, so check each museum's own website before you travel rather than trusting a page like this one.

Looking for jet on the beach

Jet is found as sea-washed pieces on the foreshore between Whitby and Ravenscar, turned out of the cliffs by the sea and rolled along the beach. Two things matter more than the finding. The cliffs on this stretch are unstable and actively fall, so digging into a cliff face is genuinely dangerous, and the tide cuts off stretches of this coast, so check tide times before you walk out and give yourself an exit. Rules about what may be collected and on whose land vary along the coast and I have not verified them, so ask locally first. The same ground and the same cautions are covered in our fossil hunting guide.