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Jet (gemstone)

(Redirected fromJet (lignite))

Jetis a type oflignite,[1]the lowestrankofcoal,and is agemstone.Unlike many gemstones, jet is not amineral,but is rather amineraloid.[2]It is derived from wood that has changed under extreme pressure.

Jet
Sample of unworked jet, about 15 mm long
General
CategoryMineraloid
Formula
(repeating unit)		Variable, but rich in carbon
Identification
ColorBlack, occasionally brown
CleavageNone
FractureConchoidal
TenacityBrittle
Mohs scalehardness2.5–4.0
StreakBrown
Specific gravity1.3–1.4
Optical propertiesIsotropic
Refractive index1.640–1.680
DispersionNone; opaque
UltravioletfluorescenceNone
Common impuritiesIron, sulfur
References[citation needed]

The English nounjetderives from the French word for the same material,jaiet(modern Frenchjais), ultimately referring to the ancient town ofGagae.[3]Jet is either black or dark brown, but may containpyriteinclusions[4]which are of brassy colour and metalliclustre.The adjective "jet-black",meaning as dark a black as possible, derives from this material.

Origin

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Jet is a product of decomposition of wood from millions of years ago, commonly the wood of trees of the familyAraucariaceae.[5]Jet is found in two forms, hard and soft.[5]Hard jet is the result of carbon compression and salt water; soft jet may be the result of carbon compression and fresh water.[5]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.[6]

Properties

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Jet is around 75% carbon and 12% oxygen with sulfur and hydrogen making up most of the balance.[7]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.[7]Jet has aMohshardnessranging between 2.5 and 4 and aspecific gravityof 1.30 to 1.34. Therefractive indexof jet is approximately 1.66. The touch of a red-hot needle should cause jet to emit an odour similar to coal.[8]

Jet may induce anelectric chargelike that of amber when rubbed.[7]

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 experiencedlapidaristto execute more elaborate carvings.

Location

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England

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A large piece of jet from Whitby

The jet found atWhitby,in England, is the "Jet Rock"[9]unit of the Mulgrave Shale Member, which is part of theWhitby Mudstone Formation.This jet deposit was formed approximately 181 million years ago, during theToarcianage of theEarly Jurassicepoch.[10][11][12]Whitby Jet is thefossilized woodfrom species similar to the extant Chilean pine (Araucaria araucana).[13]The deposit extends throughoutNorth York Moors National Park.[14]

Jet has also been found inKimmeridge shale seamsin Dorset.[15]

France

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Jet was mined from a number of areas of France includingMontjardinandRoquevaire.[16]Raw jet was also imported from Spain.[16]In the 18th century there was a jet working industry based aroundSainte-Colombe-sur-l'HersandLa Bastide-sur-l'Hersbut this declined with the start of the 19th.[16]An 1871 plan to import raw French jet into Whitby was unsuccessful due to its poor quality.[16]

Spain

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The jet found inAsturias,the biggest deposit in northern Spain,[17]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.[18]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.[19]

United States

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Native AmericanNavajoandPueblotribes ofNew Mexicowere using regionally mined jet for jewelry and the ornamentation of weapons when early Spanish explorers reached the area in the 1500s.[20]Today these jet deposits are known as Acoma jet, for theAcoma Pueblo.Enormous coal deposits characterize theSan Juan Basinof New Mexico and this geology is closely related to jet deposits mined in theHenry MountainsofUtah[21]and theFront RangeofEl Paso County,Colorado.[22]

Other locations

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Jet is also commercialized in Poland[23]and nearErzurumin Turkey, where it is known asoltu stoneand is used to makeprayer beads.[24]

History

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Three views of a prehistoric pendant in lignite/jet;Magdalenian culture(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 abotflylarva, from Baden-Württemberg, Germany, found among theVenuses of Petersfels.[25]

Jet has been used in Britain since theNeolithic period[26]It continued in use in Britain through theBronze Agewhere it was used for necklace beads.[26]Jet necklaces following the plate and spacer design may have been based onGold lunula.[27]During theIron Agejet went out of fashion until the early 3rd century AD inRoman Britain.Theend of Roman Britainmarked the end of jet's ancient popularity.[26]

Early archaeologists (particularly Victorian) often failed to distinguish between jet and other jet-like materials[28]In particular in southern Britain the material described as jet was oftenKimmeridge Shale.[28][29]and some artifacts use more than one jet-like material.[30]For example thePen y Bonc necklacecombines two or three jet pieces with other dark material.[30]

Roman use

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Whitby jet was a popular material for jewellery in Roman Britain from the 3rd century onward. There is no evidence for Roman jet working inWhitbyitself,[26]rather it was transferred toEboracum(modernYork) where considerable evidence for jet production has been found.[31]The collection of jet at this time was based onbeachcombingrather thanquarrying.[26]It was used in rings, hair pins, beads, bracelets, bangles, necklaces, and pendants,[26]many of which can be seen in theYorkshire Museum.Jet rings tended to follow the styles of existing metal rings although there were exceptions.[32]Jet pendants were carved cameo style withMedusahead being a popular theme.[33]

Stylistic similarities with jet items found in the Rhineland, and lack of any evidence for local manufacture, suggest thatEboracum-produced items were exported to that area.[34]One item that has been found around the Rhine but not in Britain are jet bracelets that feature grooves with gold inserts.[35]

Jet cameo depicting aMedusain theYorkshire Museum

The Roman period saw its use as amagicalmaterial, frequently used in amulets and pendants because of its supposed protective qualities and ability to deflect the gaze of theevil eye.[36]Pliny the Eldersuggests 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."[37]It has been referenced by other ancient writers includingSolinus[38]andGalen.

Viking use

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Vikings made some use of jet including rings and miniature sculptures of animals with snakes being a prominent theme.[39]The source of the jet has not been confirmed although Whitby is the most likely possibility.[39]

Medieval

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The Museum of London's jet bowl

Medieval jet use appears to have been largely limited to religious items such as crosses andRosarybeads.[40]During the period there was a belief that water drunk from jet bowls could help withlabour.[41]A jet bowl held in theMuseum of Londonmay have been designed to allow for this.[42]

Jet became a valued costume accessory in the 16th century.Mary, Queen of Scots,owned jet buttons and clothes embroidered with jet beads.[43]Elizabeth Ibought 1000 "black jet bugle drops" to embroider headdresses in 1587.[44]Anne of Denmarkordered a gown of "double burret" silk in June 1597 loaded with jetpassementerieand 360 jet buttons. The gown was too heavy to wear and she ordered it to be remade with less jet.[45]

Victorian use

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Mourning jewellery:jetbrooch,19th century

Jet as a gemstone became fashionable during the reign ofQueen Victoria.[46]It originally became fashionable in the 1850s after the queen wore a necklace of it as part of mourning dress forPrincess Victoria of Saxe-Coburg and Gotha.[46]Later the Queen wore Whitby jet as part of hermourning dresswhile mourning the death ofPrince Albert.[13][47][48]

In some jewellery designs of the period jet was combined withcut steel.[49]

Jet use was at its highest in the early 1870s and from there it declined.[50]From above 1000 workers in the trade Whitby was down to 300 by 1884.[50]While jet substitutes may have had an impact this appears to have been in a large part due to changes in fashion withArt Nouveaumaking little use of black jewellery.[50]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.[50]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.[50]

20th century

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an example of modern jet carving

In Whitby the Victorian tradition continued up until the aftermath of World War II.[50]Jet jewellery (both vintage and new) was then to remain out of fashion until the late '70s.[51]In the '80s there was a fashion for jet beads and antique jet jewellery started to rise in value.[52]New jewellers took up the production of jet jewellery.[52]

Jet substitutes

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Glass was used as a jet substitute during the peak of jet's popularity.[53][54]When it was used in this way it was known asFrench jetor Vauxhall glass.[53][54]Ebonitewas also used as a jet substitute and initially looks very similar to jet, but it fades over time.[55]In some cases jet offcuts were mixed with glue and molded into jewelry.[55]

Anthracite(hardcoal) 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 inepoxy resin.[56]

Authenticating jet

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Unlike blackglass,which is cool to the touch, jet is not cool, due to its lowerthermal conductivity.When rubbed against unglazed porcelain, true jet will leave a brownstreak,althoughbog oak,vulcanite,andlignitewill do the same.[57]

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.[30]

Real jet, when placed in a flame, burns like coal and gives off a coal-like smell and producessoot.No other black "gemstone" behaves like this.

See also

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References

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  1. ^Neuendorf, K. K. E. Jr.; Mehl, J. P.; Jackson, J. A., eds. (2005).Glossary of Geology(5th ed.). Alexandria, Virginia: American Geological Institute. p. 344.
  2. ^Holmes, Ralph J.; Crowningshield, Robert (1983)."Gemology".In Fyfe, Keith (ed.).The Encyclopedia of Mineralogy.Encyclopedia of Earth Sciences Series. Springer. pp.168–187.doi:10.1007/0-387-30720-6_51.ISBN978-0-87933-184-9.
  3. ^Oxford English Dictionary(2nd edition) 1989, Oxford, Oxford University Press
  4. ^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,doi:10.1017/S0016756800031496
  5. ^abcMuller, Helen; Muller, Katy (2009).Whitby Jet.Shire publications. p. 5.ISBN978-0-7478-0731-5.
  6. ^Muller, Helen (1987).Jet.Butterworths. p. 4.ISBN0-408-03110-7.
  7. ^abcMuller, Helen (1987).Jet.Butterworths. p. 2.ISBN0-408-03110-7.
  8. ^Richard T. Liddicoat, Jr.Handbook of Gem Identification1989 GIA press, 12 ed. pg 192
  9. ^Hemingway, John Edwin (1933)."Whitby jet and its relation to Upper Lias sedimentation in the Yorkshire basin".White Rose eTheses Online;PhD thesis, University of Leeds.{{cite web}}:CS1 maint: postscript (link)(SeeUpper Lias.)
  10. ^Thibault, N.; Ruhl, M.; Ullmann, C.V.; Korte, C.; Kemp, D.B.; Gröcke, D.R.; Hesselbo, S.P. (2018)."The wider context of the Lower Jurassic Toarcian oceanic anoxic event in Yorkshire coastal outcrops, UK"(PDF).Proceedings of the Geologists' Association.129(3): 372–391.Bibcode:2018PrGA..129..372T.doi:10.1016/j.pgeola.2017.10.007.S2CID55984383.
  11. ^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
  12. ^Gradstein, F.M.; Ogg, J.G.; Schmitz, M.D.; Ogg, G.M., eds. (2012).The Geologic Timescale 2012.Elsevier. p. 765.ISBN978-0-44-459390-0.
  13. ^abOliver, N., 2012,A History of Ancient Britain,Phoenix Paperback,ISBN978-0-7538-2886-1
  14. ^Muller, Helen (1987).Jet.Butterworths. p. 10.ISBN0-408-03110-7.
  15. ^Watts, S; Pollard, A.M; Wolff, G.A (1997)."Kimmeridge Jet-A Potential New Source for British Jet".Archaeometry.19(1): 125–143.doi:10.1111/j.1475-4754.1997.tb00793.x.
  16. ^abcdMuller, Helen (1987).Jet.Butterworths. pp. 112–113.ISBN0-408-03110-7.
  17. ^Ward, Gerald W. R. (2008).The Grove Encyclopedia of Materials and Techniques in Art.Oxford University Press. p. 307.ISBN978-0-19-531391-8.
  18. ^Suárez-Ruiz, Isabel; Iglesias, M. J.; Jiménez Bautista, Amalia; Domínguez Cuesta, María José; Laggoun-Défarge, F. (2006)."El azabache de Asturias: características físico-químicas, propiedades y génesis".Trabajos de Geología.26.ISSN1988-5172.
  19. ^Calvo Rebollar, Miguel (2023). "La reina Victoria y míster Goodyear. Apogeo y ocaso del azabache de Teruel".Naturaleza Aragonesa(40): 12–17.
  20. ^From The Rio To The Sierra: An Environmental History Of The Middle Rio Grande Basin(PDF).p. 103.
  21. ^Minerals and Mineral Localities of Utah(PDF).UTAH GEOLOGICAL AND MINERAL SURVEY. p. 90.
  22. ^"Jet from El Paso Co., Colorado, USA".www.mindat.org.Retrieved2019-01-25.
  23. ^Finlay, Victoria. Jewels: A Secret History (Kindle Location 1035). Random House Publishing Group. Kindle Edition.
  24. ^"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.
  25. ^"Venus figures from Petersfels".Archivedfrom the original on 29 September 2016.Retrieved9 August2016.
  26. ^abcdefAllason-Jones, Lindsay(1996).Roman Jet in the Yorkshire Museum.The Yorkshire Museum. pp. 8–11.ISBN0-905807-17-0.
  27. ^Muller, Helen (1987).Jet.Butterworths. p. 20.ISBN0-408-03110-7.
  28. ^abMuller, Helen; Muller, Katy (2009).Whitby Jet.Shire publications. pp. 7–8.ISBN978-0-7478-0731-5.
  29. ^Brück, Joanna; Davies, Alex (2018)."The Social Role of Non-metal 'Valuables' in Late Bronze Age Britain".Cambridge Archaeological Journal.28(4): 665–688.doi:10.1017/S095977431800029X.hdl:1983/bfc58ed6-3871-4e03-aa74-a27c6b815d94.S2CID165436341.
  30. ^abcSheridan, Alison; Davis, Mary (1998). "The Welsh 'jet set' in prehistory: a case of keeping up with the Joneses?".Prehistoric Ritual and Religion.Sutton. pp. 148–162.ISBN0-7509-1598-6.
  31. ^Ottaway, P., 2004,Roman York,Tempus: StroudISBN978-0-7524-2916-8
  32. ^Johns, Catherine (1996).The Jewellery of Roman Britain Celtic and classical Traditions.Routledge. pp. 69–70.ISBN978-0-415-51612-9.
  33. ^Johns, Catherine (1996).The Jewellery of Roman Britain Celtic and classical Traditions.Routledge. pp. 106–107.ISBN978-0-415-51612-9.
  34. ^Muller, Helen; Muller, Katy (2009).Whitby Jet.Shire publications. pp. 8–9.ISBN978-0-7478-0731-5.
  35. ^Johns, Catherine (1996).The Jewellery of Roman Britain Celtic and classical Traditions.Routledge. pp. 120–121.ISBN978-0-415-51612-9.
  36. ^Henig, M., 1984,Religion in Roman Britain,London, BT Batsford LtdISBN978-0-312-67059-7
  37. ^Pliny the Elder. Natural History (trans.Bostock, J.,Riley, H. T.). London: Taylor and Francis. 1855. Chapter 36
  38. ^Caius Julius Solinus (2013)."DE MIRABILIBUS MUNDI CAPITULA VII–XXIV".Archivedfrom the original on 2013-02-06.Retrieved2013-10-31.
  39. ^abMuller, Helen (1987).Jet.Butterworths. pp. 25–26.ISBN0-408-03110-7.
  40. ^Muller, Helen (1987).Jet.Butterworths. pp. 27–28.ISBN0-408-03110-7.
  41. ^French, Katherine L (2021).Household Goods and Good Households in Late Medieval London Consumption and Domesticity After the Plague.University of Pennsylvania Press, Incorporated. p. 141.ISBN978-0-8122-5305-4.
  42. ^Gilchrist, Roberta (2012).Medieval Life Archaeology and the Life Course.Boydell Press. p. 141.ISBN978-1-84383-722-0.
  43. ^Alexandre Labanoff,Lettres de Marie Stuart,vol. 7 (London: Dolman, 1844), pp. 230-238.
  44. ^Janet Arnold,Queen Elizabeth's Wardrobe Unlock'd(Maney, 1988), p. 205.
  45. ^Jemma Field,'Female dress', Erin Griffey, Early Modern Court Culture (Routledge, 2022), pp. 398-99.
  46. ^abTolkien, Tracy; Wilkinson, Henrietta (1997).A Collector's Guide to Costume Jewelry Key Styles and how to recognize them.Firefly Books. p. 52.ISBN1-55209-156-2.
  47. ^St. Clair, Kassia (2016).The Secret Lives of Colour.London: John Murray. pp. 276–277.ISBN978-1-4736-3081-9.OCLC936144129.
  48. ^Phillips, Clare (1996).Jewelry from Antiquity to the Present.Thames and Hudson. pp.148–150.ISBN978-0-500-20287-6.
  49. ^Clifford, Anne (1971).Cut-Steel and Berlin Iron Jewellery.Adams & Dart. pp. 21–22.ISBN978-0-239-00069-9.
  50. ^abcdefMuller, Helen (1987).Jet.Butterworths. pp. 59–63.ISBN0-408-03110-7.
  51. ^Muller, Helen (1987).Jet.Butterworths. p. 60.ISBN0-408-03110-7.
  52. ^abMuller, Helen (1987).Jet.Butterworths. p. 64.ISBN0-408-03110-7.
  53. ^ab"Jet necklace and black silk tie".Body arts.Pitt Rivers Museum. 2011.Archivedfrom the original on 16 February 2016.Retrieved9 February2016.
  54. ^ab"Tiara".V&A Collections.Victoria and Albert Museum.Archivedfrom the original on 15 February 2016.Retrieved9 February2016.
  55. ^abPhillips, Clare (1996).Jewelry from Antiquity to the Present.Thames and Hudson. p.150.ISBN978-0-500-20287-6.
  56. ^Muller, Helen (1987).Jet.Butterworths. p. 129.ISBN0-408-03110-7.
  57. ^Muller, Helen (1987).Jet.Butterworths. p. 132.ISBN0-408-03110-7.
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