What Is Jet Jewellery?

Jet is a dense, black, organic gemstone material formed from fossilised wood, valued in jewellery for its deep colour, light weight and capacity to take a very high polish.

What Jet Is

Jet is a type of lignite - a low grade of coal - formed when waterlogged driftwood, typically from an ancient monkey-puzzle-like tree, was compressed and mineralised over millions of years. Unlike most gemstone materials, it is not a mineral crystal but a compact, fine-grained organic substance, which is why it can be carved, turned and polished more like a hard wood than cut like a faceted stone. The jet of the Yorkshire coast formed in the Jurassic period, around 180 million years ago, and the trees that produced it were relatives of the modern monkey-puzzle (the Araucaria family). Jet-workers distinguish “hard jet”, which is tough and keeps its polish, from “soft jet”, which formed in different conditions and is more likely to crack or craze over time. Good-quality jet is remarkably light for its size, faintly warm rather than cold to the touch, and takes a deep, glossy black polish, though it can also be left with a soft matte finish.

How It Was Worked

Jet was carved, turned on a lathe, and polished using techniques closer to woodworking than traditional lapidary or metalworking, which suited it to small workshops producing carved beads, cameos, and elaborately faceted mourning brooches and bracelets in large quantities. Its softness relative to true minerals made it comparatively easy to carve in detail but also more vulnerable to scratching and chipping than harder gemstone materials, a fragility still relevant to how surviving pieces are handled today.

A Long History Before Mourning Fashion

Jet’s use in ornament considerably predates its Victorian heyday:

• Prehistory. In Early Bronze Age Britain, around 2000 BC, jet was made into elaborate crescent-shaped necklaces of beads strung through spacer plates, found in burials in Scotland and northern England.
• Roman Britain. Craftsmen at York (Eboracum) carved Yorkshire jet into beads, bracelets, finger rings, hairpins and medallions with portraits or paired heads, mainly in the 3rd and 4th centuries AD. Jet’s static charge when rubbed, which seemed magical, gave it a reputation as a protective material.
• Medieval Spain. At Santiago de Compostela, jet carvers made figures of St James and other devotional objects as pilgrim souvenirs, using jet (azabache) from Asturias in northern Spain.
• 17th and 18th centuries. Jet was used for rosaries, crosses and some mourning jewellery, though in 18th-century Britain black enamel and black glass were more usual for mourning.

Where Jet Came From

The most important source for British jewellery was the Yorkshire coast around Whitby, where an industry of carvers grew up in the 19th century; see Whitby Jet and Victorian Jewellery. Spain, particularly Asturias, had its own long jet tradition and exported jet in the later 19th century, including to Whitby workshops when local supplies ran short. Jet was also worked in the Aude region of southern France from the medieval period into the 18th century, and a jet-like lignite from north-eastern Turkey was carved into prayer beads. Spanish and other imported jet was generally considered softer and more prone to cracking than the best Whitby hard jet.

The Victorian Mourning Boom

Jet’s association with black, sober adornment made it the material of choice for mourning jewellery once Victorian mourning customs intensified demand for appropriately restrained jewellery, especially after Prince Albert’s death in 1861, when Queen Victoria and her court entered prolonged mourning and jet became the jewellery most acceptable during the deeper stages of mourning. Genuine jet was, however, a natural material of limited and variable supply, and the resulting demand for cheap black jewellery outstripped what could be carved from it - opening the way for close imitations made from other materials.

Jet’s Common Imitations

Two materials were especially widely used to imitate jet in the 19th century: vulcanite, an early hard rubber that could be moulded and dyed black, and French jet, which despite its name is a black glass or glass paste, cut and polished to catch light in a way that carved jet, with its softer sheen, generally does not. Neither is inherently poor-quality - both were produced to a high standard and are collected in their own right - but distinguishing them from genuine jet matters for accurate identification and dating.

Other Black Materials

Vulcanite and French jet were the most common substitutes, but several other black materials turn up in Victorian mourning and half-mourning jewellery:

• Bog oak - ancient oak preserved and blackened in Irish peat bogs, carved or pressed into brooches and bracelets with Irish motifs such as shamrocks, harps and round towers. It is dark brown-black rather than true black, and wood grain is usually visible under a loupe.
• Gutta-percha - a natural latex moulded like vulcanite and used for similar inexpensive pieces. It is often brownish and can become brittle with age.
• Black onyx - dyed black chalcedony, cut and polished as plaques, beads and cabochons. It is heavy, cold and hard, with a glassy polish, and was used in fine mourning jewellery with gold and pearls.
• Black enamel - a fused glass coating on gold, used for the inscriptions and borders of mourning rings and lockets; see What Is a Mourning Ring?.
• Pressed horn - horn softened and moulded under heat into brooches and buttons, sometimes dyed black.
• Berlin iron - cast iron lacquered black, from earlier in the century. Unlike every other material here, it is attracted to a magnet; see What Is Berlin Iron Jewellery?.

Moulded materials - vulcanite, gutta-percha and pressed horn - can often be recognised by identical repeated designs, soft rounded detail and occasional mould seams, whereas jet was carved or faceted by hand. Avoid destructive tests such as touching a hot needle to the back of a piece: they damage the surface and are no more reliable than careful observation.

How to Recognise Genuine Jet

In combination, light weight, a faint warmth to the touch, a duller resinous sheen rather than glassy brilliance, and a soft rather than sharp sound when gently tapped against a tooth are the features most often cited for distinguishing carved jet from its imitations. As with all material identification questions, these are useful starting points rather than certain tests, and a piece that matters - for insurance, sale or family history - is best assessed by a specialist experienced in organic gemstone materials.

Frequently Asked Questions

Is all antique black jewellery made of jet? No - vulcanite and French jet were both produced in enormous quantities alongside genuine jet, and black onyx, black enamel and dyed horn also appear in black jewellery of the period, so material identification generally needs more than colour alone.

Does jet need special care? Jet is comparatively soft and can be scratched, chipped or dulled by harsh cleaning agents, so gentle handling and avoiding household chemicals or ultrasonic cleaners is generally recommended for antique jet jewellery.