MarketJet (gemstone)
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Jet (gemstone)

Jet is a type of lignite, the lowest rank of coal, and is a gemstone. Unlike many gemstones, jet is not a mineral, but is rather a mineraloid. It is derived from wood that has changed under extreme pressure.

Origin
Jet is a product of decomposition of wood from millions of years ago, commonly the wood of trees of the family Araucariaceae. Despite the name they both occupy the same area of the Mohs scale with the difference being that soft jet is more likely to crack when exposed to changes in temperature. ==Properties==
Properties
Jet is around 75% carbon and 12% oxygen with sulfur and hydrogen making up most of the balance. Jet may induce an electric charge like that of amber when rubbed. Jet is very easily cut using carving tools, but small pieces tend to break off, making it difficult to create fine details. It therefore takes an experienced lapidarist to execute more elaborate carvings. ==Location==
Location
England The jet found at Whitby, in England, is the "Jet Rock" unit of the Mulgrave Shale Member, which is part of the Whitby Mudstone Formation. This jet deposit was formed approximately 181 million years ago, during the Toarcian age of the Early Jurassic epoch. Whitby Jet is the fossilized wood from species similar to the extant Chilean pine (Araucaria araucana). The deposit extends throughout North York Moors National Park. Jet has also been found in Kimmeridge shale seams in Dorset. France Jet was mined from a number of areas of France including Montjardin and Roquevaire. Spain The jet found in Asturias, the biggest deposit in northern Spain, is of Late Jurassic (Kimmeridgian) age, about 155 million years old. Asturian jet is a perhydrous coal that suffered an anomalous coalification process and presents great material stability over long periods of time. At the end of the Middle Ages, the trade of religious objects and amulets made of jet reached great development in Santiago de Compostela, with sales to pilgrims traveling the Camino de Santiago. However, the deposits were in Asturias, where simple objects such as beads and rosary beads were also made. Santiago de Compostela was the main sales point and the location of the workshops that produced artistic objects. Jet has also been extracted in the area of Utrillas, Gargallo, and Montalbán in the province of Teruel, although it is of lower quality than that from Asturias. United States Native American Navajo and Pueblo tribes of New Mexico were using regionally mined jet for jewelry and the ornamentation of weapons when early Spanish explorers reached the area in the 1500s. Today these jet deposits are known as Acoma jet, for the Acoma Pueblo. Enormous coal deposits characterize the San Juan Basin of New Mexico and this geology is closely related to jet deposits mined in the Henry Mountains of Utah and the Front Range of El Paso County, Colorado. Other locations Jet is also commercialized in Poland and near Erzurum in Turkey, where it is known as oltu stone and is used to make prayer beads. ==History==
History
(17,000–10,000 BC), from the Marsoulas cave, Marsoulas, Haute-Garonne, France The earliest known worked jet object is a 10,000 BC model of a botfly larva, from Baden-Württemberg, Germany, found among the Venuses of Petersfels. Jet has been used in Britain since the Neolithic period It continued in use in Britain through the Bronze Age where it was used for necklace beads. During the Iron Age jet went out of fashion until the early 3rd century AD in Roman Britain. The end of Roman Britain marked the end of jet's ancient popularity. and some artifacts use more than one jet-like material. Roman use Whitby jet was a popular material for jewellery in Roman Britain from the 3rd century onward. There is no evidence for Roman jet working in Whitby itself, The collection of jet at this time was based on beachcombing rather than quarrying. Jet pendants were carved cameo style with Medusa head being a popular theme. Stylistic similarities with jet items found in the Rhineland, and lack of any evidence for local manufacture, suggest that Eboracum-produced items were exported to that area. One item that has been found around the Rhine but not in Britain are jet bracelets that feature grooves with gold inserts. in the Yorkshire Museum The Roman period saw its use as a magical material, frequently used in amulets and pendants because of its supposed protective qualities and ability to deflect the gaze of the evil eye. Pliny the Elder suggests that "the kindling of jet drives off snakes and relieves suffocation of the uterus. Its fumes detect attempts to simulate a disabling illness or a state of virginity." It has been referenced by other ancient writers including Solinus and Galen. Viking use Vikings made some use of jet including rings and miniature sculptures of animals with snakes being a prominent theme. Medieval Medieval jet use appears to have been largely limited to religious items such as crosses and Rosary beads. During the period there was a belief that water drunk from jet bowls could help with labour. A 15th century jet bowl held in the Museum of London may have been designed to allow for this. Jet became a valued costume accessory in the 16th century. Mary, Queen of Scots, owned jet buttons and clothes embroidered with jet beads. Elizabeth I bought 1000 "black jet bugle drops" to embroider headdresses in 1587. Anne of Denmark ordered a gown of "double burret" silk in June 1597 loaded with jet passementerie and 360 jet buttons. The gown was too heavy to wear and she ordered it to be remade with less jet. Victorian use : jet brooch, 19th century Jet as a gemstone became fashionable as mourning jewellery during the reign of Queen Victoria. Later the Queen wore Whitby jet as part of her mourning dress while mourning the death of Prince Albert. In some jewellery designs of the period jet was combined with cut steel. Jet use was at its highest in the early 1870s and from there it declined. 20th century In Whitby the Victorian tradition continued up until the aftermath of World War II. In the '80s there was a fashion for jet beads and antique jet jewellery started to rise in value. ==Jet substitutes==
Jet substitutes
Glass was used as a jet substitute during the peak of jet's popularity. Ebonite was also used as a jet substitute and initially looks very similar to jet, but it fades over time. Anthracite (hard coal) is superficially similar to fine jet, and has been used to imitate it. This imitation is not always easy to distinguish from real jet. Some museums have produced reproductions of jet artefacts in epoxy resin. ==Authenticating jet==
Authenticating jet
Unlike black glass, which is cool to the touch, jet is not cool, due to its lower thermal conductivity. When rubbed against unglazed porcelain, true jet will leave a brown streak, although bog oak, vulcanite, and lignite will do the same. When non-destructive testing is required, X-ray fluorescence spectroscopy, combined with visual inspection (including under high magnification) and X-ray imaging, is generally effective, although it can be difficult to differentiate jet from lignite. Real jet, when placed in a flame, burns like coal and gives off a coal-like smell and produces soot. No other black "gemstone" behaves like this. ==See also==
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