A sample of jet

Hallstatt culture bracelets made from jet and bronze, unearthed at Magdalenenberg

Mourning jewellery: Jet Brooch, 19th century.

Jet is a geological material and is considered to be a minor gemstone. Jet is not considered a true mineral, but rather a mineraloid as it has an organic origin, being derived from decaying wood under extreme pressure.

The English noun "jet" derives from the French word for the same material: jaiet^[1]. Jet is either black or dark brown, but may contain pyrite inclusions, which are of brassy color and metallic lustre. The adjective jet-black is better known perhaps than the substance from which the descriptive phrase derives.

[edit] Origin

Jet is a product of high pressure decomposition of wood from millions of years ago, commonly the wood of trees of the Araucariaceae family. Jet is found in two forms, hard and soft. Hard jet is the result of the carbon compression and salt water; soft jet is the result of the carbon compression and fresh water. Jet is easily polished and is used in manufacturing jewellery, according to the Whitby Museum, dating from 10,000 BC in parts of contemporary Germany. The oldest jet jewellery was found in Asturias, Spain, dating from 17,000 BC.

[edit] History

Jet as a gem material was highly popular during the reign of Queen Victoria, during which the Queen wore Whitby jet as part of her mourning dress. Jet was popular for mourning jewellery in the 19th century because of its sombre color and modest appearance, and it has been traditionally fashioned into rosaries for monks. In the United States, long necklaces of jet beads were very popular during the 1920s, or Roaring Twenties, when women and young flappers would wear multiple strands of jet beads stretching from the neckline to the waistline. In these necklaces, the jet was strung using heavy cotton thread; small knots were made on either side of each bead to keep the beads spaced evenly, much in the same way that fine pearl necklaces are made. Jet has also been known as black amber, as it may induce an electric charge like that of amber when rubbed.

A large piece of jet from Whitby. The coin is 23 mm or just less than one inch across.

[edit] Authenticating jet

Although now much less popular than in the past, authentic jet jewels are valued by collectors.

Unlike black glass, which is cool to the touch, jet is not cool, due to its lesser thermal conductivity.

Anthracite (hard coal) and Vulcanite (hardened rubber) are superficially similar to fine jet, and have been used to imitate it. These imitations are not always easy to distinguish from the real thing.

The structure of jet (which is remarkably like the wood that it is derived from) can be seen under 120x or greater magnification.

[edit] References

Wikimedia Commons has media related to: Jet

1. ^ Oxford English Dictionary (2nd edition) 1989, Oxford, Oxford University Press

[edit] External links

• Whitby Jet
• Jet, the fossilized wood, the Asturian Jet in the Jurassic.