Jet (gemstone)
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Jet is a type of lignite,<ref name="Glossary2005">Template:Cite book</ref> the lowest rank of coal, and is a gemstone. Unlike many gemstones, jet is not a mineral, but is rather a mineraloid.<ref>Template:Cite encyclopedia</ref> It is derived from wood that has changed under extreme pressure.
The English noun jet derives from the French word for the same material, {{#invoke:Lang|lang}} (modern French Template:Wikt-lang), ultimately referring to the ancient town of Gagae.<ref>Oxford English Dictionary (2nd edition) 1989, Oxford, Oxford University Press</ref> Jet is either black or dark brown, but may contain pyrite inclusions<ref>Pye, K. (1985). "Electron microscope analysis of zoned dolomite rhombs in the Jet Rock Formation (Lower Toarcian) of the Whitby area, U.K.", Geological Magazine, volume 122, issue 3, pp. 279–286, Cambridge University Press, {{#invoke:doi|main}}</ref> which are of brassy colour and metallic lustre. The adjective "jet-black", meaning as dark a black as possible, derives from this material.
OriginEdit
Jet is a product of decomposition of wood from millions of years ago, commonly the wood of trees of the family Araucariaceae.<ref name=muller5 /> Jet is found in two forms, hard and soft.<ref name=muller5 /> Hard jet is the result of carbon compression and salt water; soft jet may be the result of carbon compression and fresh water.<ref name=muller5>Template:Cite book</ref> 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.<ref name=MullerH4>Template:Cite book</ref>
PropertiesEdit
Jet is around 75% carbon and 12% oxygen with sulfur and hydrogen making up most of the balance.<ref name=MullerH2 /> Other elements are found at trace level and the exact ratios varying with the source; for example, Spanish jet contains more sulfur than Whitby jet.<ref name=MullerH2 /> Jet has a Mohs hardness ranging between 2.5 and 4 and a specific gravity of 1.30 to 1.34. The refractive index of jet is approximately 1.66. The touch of a red-hot needle should cause jet to emit an odour similar to coal.<ref>Richard T. Liddicoat, Jr. Handbook of Gem Identification 1989 GIA press, 12 ed. pg 192</ref>
Jet may induce an electric charge like that of amber when rubbed.<ref name=MullerH2>Template:Cite book</ref>
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.
LocationEdit
EnglandEdit
The jet found at Whitby, in England, is the "Jet Rock"<ref>{{#invoke:citation/CS1|citation |CitationClass=web }} (See Upper Lias.)</ref> 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.<ref name="Thibault-et-al-2018">Template:Cite journal</ref><ref>Cope, J. C. W. (2006). Jurassic: the returning seas - plate 26 and page 339 of Brenchley, P. J. and Rawson P. F. (editors) (2006) The Geology of England and Wales, 2nd edition, London, The Geological Society</ref><ref name="Gradstein_et-al_2012">Template:Cite book</ref> Whitby Jet is the fossilized wood from species similar to the extant Chilean pine (Araucaria araucana).<ref name=Oliver>Oliver, N., 2012, A History of Ancient Britain, Phoenix Paperback, Template:ISBN</ref> The deposit extends throughout North York Moors National Park.<ref name=MullerH10>Template:Cite book</ref>
Jet has also been found in Kimmeridge shale seams in Dorset.<ref name=Watts>Template:Cite journal</ref>
FranceEdit
Jet was mined from a number of areas of France including Montjardin and Roquevaire.<ref name=MullerH112 /> Raw jet was also imported from Spain.<ref name=MullerH112 /> In the 18th century there was a jet working industry based around Sainte-Colombe-sur-l'Hers and La Bastide-sur-l'Hers but this declined with the start of the 19th.<ref name=MullerH112 /> An 1871 plan to import raw French jet into Whitby was unsuccessful due to its poor quality.<ref name=MullerH112>Template:Cite book</ref>
SpainEdit
The jet found in Asturias, the biggest deposit in northern Spain,<ref>Template:Cite book</ref> 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.<ref>Template:Cite journal</ref> 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.<ref>Template:Cite journal</ref>
United StatesEdit
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.<ref>Template:Cite book</ref> 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<ref name="Utah">Template:Cite book</ref> and the Front Range of El Paso County, Colorado.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Other locationsEdit
Jet is also commercialized in Poland<ref>Finlay, Victoria. Jewels: A Secret History (Kindle Location 1035). Random House Publishing Group. Kindle Edition.</ref> and near Erzurum in Turkey, where it is known as oltu stone and is used to make prayer beads.<ref>"While there is no source of jet anywhere near southwestern Turkey, it can be found in western Anatolia near Erzurum, where there are about six hundred family-run mines in the mountains. They call it oltu-tasi and it is the material from which Muslim prayer-beads are made. Finlay, Victoria. Jewels: A Secret History (Kindle Locations 1054-1056). Random House Publishing Group. Kindle Edition.</ref>
HistoryEdit
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.<ref name="botfly">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Jet has been used in Britain since the Neolithic period<ref name=RomanJet8>Template:Cite book</ref> It continued in use in Britain through the Bronze Age where it was used for necklace beads.<ref name=RomanJet8 /> Jet necklaces following the plate and spacer design may have been based on Gold lunula.<ref name=MullerH20>Template:Cite book</ref> 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.<ref name=RomanJet8 />
Early archaeologists (particularly Victorian) often failed to distinguish between jet and other jet-like materials <ref name=muller7 /> In particular in southern Britain the material described as jet was often Kimmeridge Shale.<ref name=muller7>Template:Cite book</ref><ref name=Brück>Template:Cite journal</ref> and some artifacts use more than one jet-like material.<ref name=Sheridan /> For example, the Pen y Bonc necklace combines two or three jet pieces with other dark material.<ref name=Sheridan>Template:Cite book</ref>
Roman useEdit
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,<ref name=RomanJet8 /> rather it was transferred to Eboracum (modern York) where considerable evidence for jet production has been found.<ref name="RomanYork">Ottaway, P., 2004, Roman York, Tempus: Stroud Template:ISBN</ref> The collection of jet at this time was based on beachcombing rather than quarrying.<ref name=RomanJet8 /> It was used in rings, hair pins, beads, bracelets, bangles, necklaces, and pendants,<ref name=RomanJet8 /> many of which can be seen in the Yorkshire Museum. Jet rings tended to follow the styles of existing metal rings although there were exceptions.<ref name=johns69>Template:Cite book</ref> Jet pendants were carved cameo style with Medusa head being a popular theme.<ref name=johns106>Template:Cite book</ref>
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.<ref name=muller8>Template:Cite book</ref> One item that has been found around the Rhine but not in Britain are jet bracelets that feature grooves with gold inserts.<ref name=johns120>Template:Cite book</ref>
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.<ref>Henig, M., 1984, Religion in Roman Britain, London, BT Batsford Ltd Template:ISBN</ref> 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."<ref>Pliny the Elder. Natural History (trans. Bostock, J., Riley, H. T.). London: Taylor and Francis. 1855. Chapter 36</ref> It has been referenced by other ancient writers including Solinus<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and Galen.
Viking useEdit
Vikings made some use of jet including rings and miniature sculptures of animals with snakes being a prominent theme.<ref name=MullerH25 /> The source of the jet has not been confirmed although Whitby is the most likely possibility.<ref name=MullerH25>Template:Cite book</ref>
MedievalEdit
Medieval jet use appears to have been largely limited to religious items such as crosses and Rosary beads.<ref name=MullerH27>Template:Cite book</ref> During the period there was a belief that water drunk from jet bowls could help with labour.<ref name=French>Template:Cite book</ref> A jet bowl held in the Museum of London may have been designed to allow for this.<ref name=Gilchrist>Template:Cite book</ref>
Jet became a valued costume accessory in the 16th century. Mary, Queen of Scots, owned jet buttons and clothes embroidered with jet beads.<ref>Alexandre Labanoff, Lettres de Marie Stuart, vol. 7 (London: Dolman, 1844), pp. 230-238.</ref> Elizabeth I bought 1000 "black jet bugle drops" to embroider headdresses in 1587.<ref>Janet Arnold, Queen Elizabeth's Wardrobe Unlock'd (Maney, 1988), p. 205.</ref> 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.<ref>Jemma Field, 'Female dress', Erin Griffey, Early Modern Court Culture (Routledge, 2022), pp. 398-99.</ref>
Victorian useEdit
Jet as a gemstone became fashionable during the reign of Queen Victoria.<ref name=Tolkien52 /> It originally became fashionable in the 1850s after the queen wore a necklace of it as part of mourning dress for Princess Victoria of Saxe-Coburg and Gotha.<ref name=Tolkien52>Template:Cite book</ref> Later the Queen wore Whitby jet as part of her mourning dress while mourning the death of Prince Albert.<ref name=Oliver/><ref name="StClair">Template:Cite book</ref><ref name=Phillips1148>Template:Cite book</ref>
In some jewellery designs of the period jet was combined with cut steel.<ref name=Clifford21>Template:Cite book</ref>
Jet use was at its highest in the early 1870s and from there it declined.<ref name=MullerH59 /> From above 1000 workers in the trade Whitby was down to 300 by 1884.<ref name=MullerH59 /> While jet substitutes may have had an impact this appears to have been in a large part due to changes in fashion with Art Nouveau making little use of black jewellery.<ref name=MullerH59 /> As the numbers fell the remaining manufactures tended to stick with existing styles rather than attempting to adapt to new fashions resulting in demand falling further.<ref name=MullerH59 /> Making tourist trinkets kept a few jewellers in work, but by the end of World War II only three remained, and the industry died out completely with their deaths.<ref name=MullerH59>Template:Cite book</ref>
20th centuryEdit
In Whitby the Victorian tradition continued up until the aftermath of World War II.<ref name=MullerH59 /> Jet jewellery (both vintage and new) was then to remain out of fashion until the late '70s.<ref name=MullerH60>Template:Cite book</ref> In the '80s there was a fashion for jet beads and antique jet jewellery started to rise in value.<ref name=MullerH64 /> New jewellers took up the production of jet jewellery.<ref name=MullerH64>Template:Cite book</ref>
Jet substitutesEdit
Glass was used as a jet substitute during the peak of jet's popularity.<ref name=frenchj /><ref name=V&AT /> When it was used in this way it was known as French jet or Vauxhall glass.<ref name=frenchj>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=V&AT>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Ebonite was also used as a jet substitute and initially looks very similar to jet, but it fades over time.<ref name=Phillips150 /> In some cases jet offcuts were mixed with glue and molded into jewelry.<ref name=Phillips150>Template:Cite book</ref>
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.<ref name=MullerH129>Template:Cite book</ref>
Authenticating jetEdit
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.<ref name=MullerH132>Template:Cite book</ref>
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.<ref name=Sheridan />
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.