Jet is a type of
lignite,
the lowest
rank
Rank is the relative position, value, worth, complexity, power, importance, authority, level, etc. of a person or object within a ranking, such as:
Level or position in a hierarchical organization
* Academic rank
* Diplomatic rank
* Hierarchy
* ...
of
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when ...
, and is a
gemstone. Unlike many gemstones, jet is not a
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
, but is rather a
mineraloid. It is derived from wood that has changed under extreme pressure.
The English noun ''jet'' derives from the French word for the same material, (modern French ), ultimately referring to the ancient town of
Gagae
Gagae or Gagai ( grc, Γάγαι) was a town on the southeast coast of ancient Lycia, in what is now the province of Antalya, from which the ''Gagates lapis'' derived its name. The ruins are located in Kumluca district, Antalya Province, Turkey. ...
. Jet is either black or dark brown, but may contain
pyrite
The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic luster and pale brass-yellow hue giv ...
inclusions which are of brassy colour and metallic
lustre
Lustre or Luster may refer to:
Places
* Luster, Norway, a municipality in Vestlandet, Norway
** Luster (village), a village in the municipality of Luster
* Lustre, Montana, an unincorporated community in the United States
Entertainment
* '' ...
. The adjective "
jet-black", meaning as dark a black as possible, derives from this material.
Origin
Jet is a product of decomposition of wood from millions of years ago, commonly the wood of trees of the family
Araucariaceae
Araucariaceae – also known as araucarians – is an extremely ancient family of coniferous trees. The family achieved its maximum diversity during the Jurassic and Cretaceous periods and the early Cenozoic, when it was distributed almost worldw ...
.
Jet is found in two forms, hard and soft.
Hard jet is the result of carbon compression and salt water; soft jet may be the result of carbon compression and fresh water.
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
Jet is around 75% carbon and 12% oxygen with sulfur and hydrogen making up most of the balance.
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.
Jet has a
Mohs hardness
In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...
ranging between 2.5 and 4 and a
specific gravity
Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its densest ...
of 1.30 to 1.34. The
refractive index
In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium.
The refractive index determines how much the path of light is bent, or ...
of jet is approximately 1.66. The touch of a red-hot needle should cause jet to emit an odour similar to coal.
Jet may induce an
electric charge
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...
like that of amber when rubbed.
Jet is very easy to carve, but it is difficult to create fine details without breaking so it takes an experienced
lapidarist
Lapidary (from the Latin ) is the practice of shaping stone, minerals, or gemstones into decorative items such as cabochons, engraved gems (including cameos), and faceted designs. A person who practices lapidary is known as a lapidarist. A lap ...
to execute more elaborate carvings.
Location
England
![Whitby-Jet](https://upload.wikimedia.org/wikipedia/commons/e/e2/Whitby-Jet.jpg)
The jet found at
Whitby
Whitby is a seaside town, port and civil parish in the Scarborough borough of North Yorkshire, England. Situated on the east coast of Yorkshire at the mouth of the River Esk, Whitby has a maritime, mineral and tourist heritage. Its East Clif ...
, in England, is the "''Jet Rock''" unit of the Mulgrave Shale Member, which is part of the
Whitby Mudstone Formation
The Whitby Mudstone is a Toarcian (Early Jurassic; ''Falciferum''-''Bifrons'' in regional chronostratigraphy) geological formation in Yorkshire and Worcestershire, England.[Toarcian
The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian.
The Toarcian ...]
age of the
Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
epoch.
Whitby Jet is the fossilized wood from species similar to the extant Chilean pine (''
Araucaria araucana
''Araucaria araucana'' (commonly called the monkey puzzle tree, monkey tail tree, piñonero, pewen or Chilean pine) is an evergreen tree growing to a trunk diameter of 1–1.5 m (3–5 ft) and a height of 30–40 m (100–130 ft). ...
'').
[Oliver, N., 2012, ''A History of Ancient Britain'', Phoenix Paperback, ] The deposit extends throughout
North York Moors National Park
North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography.
Etymology
The word ''north'' is ...
.
Jet has also been found in
Kimmeridge shale seams in Dorset.
France
Jet was mined from a number of areas of France including
Montjardin
Montjardin () is a commune in the Aude department in southern France. Historically jet was mined in this area. Population
See also
*Communes of the Aude department
The following is a list of the 433 communes of the Aude department of Fr ...
and
Roquevaire
Roquevaire (; oc, Ròcavaira) is a commune in the Huveaune valley between Aubagne and Auriol in the Bouches-du-Rhône department in the Provence-Alpes-Côte d'Azur region of Southern France. In 2017, it had a population of 9,003. Its inhabita ...
.
Raw jet was also imported from Spain.
In the 18th century there was a jet working industry based around
Sainte-Colombe-sur-l'Hers
Sainte-Colombe-sur-l'Hers (, literally ''Sainte-Colombe on the Hers''; Languedocien: ''Santa Colomba d'Ers'' or ''Santa Colomba d'Èrs'') is a commune in the Aude department in southern France.
Population
See also
*Communes of the Aude de ...
and
La Bastide-sur-l'Hers
La Bastide-sur-l'Hers (, literally ''La Bastide on the Hers''; oc, La Bastida d'Èrç) is a commune in the Ariège department in the Occitanie region of southwestern France.
The inhabitants of the commune are known as ''Bastidhersois'' or '' ...
but this declined with the start of the 19th.
An 1871 plan to import raw French jet into Whitby was unsuccessful due to its poor quality.
Spain
The jet found in
Asturias
Asturias (, ; ast, Asturies ), officially the Principality of Asturias ( es, Principado de Asturias; ast, Principáu d'Asturies; Galician-Asturian: ''Principao d'Asturias''), is an autonomous community in northwest Spain.
It is coextensiv ...
, the biggest deposit in northern Spain, is of Late Jurassic (
Kimmeridgian
In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxford ...
) 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.
Jet is also found near
Santiago de Compostela
Santiago de Compostela is the capital of the autonomous community of Galicia, in northwestern Spain. The city has its origin in the shrine of Saint James the Great, now the Cathedral of Santiago de Compostela, as the destination of the Way of S ...
in northwest Spain
United States
Native American
Navajo and
Pueblo
In the Southwestern United States, Pueblo (capitalized) refers to the Native tribes of Puebloans having fixed-location communities with permanent buildings which also are called pueblos (lowercased). The Spanish explorers of northern New Spain ...
tribes of
New Mexico
)
, population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano)
, seat = Santa Fe
, LargestCity = Albuquerque
, LargestMetro = Tiguex
, OfficialLang = None
, Languages = English, Spanish ( New Mexican), Navajo, Ke ...
were using regionally mined jet for jewellery 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
Acoma Pueblo (, kjq, Áakʼu) is a Native American pueblo approximately west of Albuquerque, New Mexico, in the United States. Four communities make up the village of Acoma Pueblo: Sky City (Old Acoma), Acomita, Anzac, and McCartys. These co ...
. Enormous coal deposits characterize the
San Juan Basin
The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah ...
of New Mexico and this geology is closely related to jet deposits mined in the
Henry Mountains
The Henry Mountains is a mountain range located in the southeastern portion of the U.S. state of Utah that runs in a generally north-south direction, extending over a distance of about . They were named by Almon Thompson in honor of Joseph Henry ...
of
Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
and the
Front Range
The Front Range is a mountain range of the Southern Rocky Mountains of North America located in the central portion of the U.S. State of Colorado, and southeastern portion of the U.S. State of Wyoming. It is the first mountain range encountered ...
of
El Paso County,
Colorado
Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...
.
Other locations
Jet is also commercialized in Poland and near
Erzurum
Erzurum (; ) is a city in eastern Anatolia, Turkey. It is the largest city and capital of Erzurum Province and is 1,900 meters (6,233 feet) above sea level. Erzurum had a population of 367,250 in 2010.
The city uses the double-headed eagle as ...
in Turkey, where it is known as
oltu stone
Oltu stone ( tr, Oltu taşı) is a kind of jet (lignite), jet found in the region around Oltu town within Erzurum Province, eastern Turkey. The organic substance is used as semi-precious gemstone in manufacturing jewellery.
Location and extracti ...
and is used to make
prayer beads
Prayer beads are a form of beadwork used to count the repetitions of prayers, chants, or mantras by members of various religions such as Hinduism, Buddhism, Shinto, Umbanda, Islam, Sikhism, the Baháʼí Faith, and some Christian denominati ...
.
History
![Pendeloque en lignite Marsoulas MHNT](https://upload.wikimedia.org/wikipedia/commons/2/26/Pendeloque_en_lignite_Marsoulas_MHNT.PRE.2012.0.6.95.jpg)
The earliest known worked jet object is a 10,000 BC model of a
botfly
Botflies, also known as warble flies, heel flies, and gadflies, are a family of flies known as the Oestridae. Their larvae are internal parasites of mammals, some species growing in the host's flesh and others within the gut. '' Dermatobia hom ...
larva, from Baden-Württemberg, Germany, found among the
Venuses of Petersfels
__NOTOC__
The Venus figurines of Petersfels are several small female statuettes from the Upper Paleolithic art, Upper Paleolithic era, carved from jet (lignite), jet lignite. The tallest figurine is called the Venus of Engen. The figurines were d ...
.
Jet has been used in Britain since the
Neolithic period
The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several parts ...
It continued in use in Britain through the
Bronze Age
The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second prin ...
where it was used for necklace beads.
Jet necklaces following the plate and spacer design may have been based on
Gold lunula
The Gold lunula (plural: lunulae) is a distinctive type of late Neolithic, Chalcolithic or (most often) early Bronze Age necklace or collar shaped like a crescent moon; most are from Prehistoric Ireland. They are normally flat and thin, with ...
.
During the
Iron Age
The Iron Age is the final epoch of the three-age division of the prehistory and protohistory of humanity. It was preceded by the Stone Age ( Paleolithic, Mesolithic, Neolithic) and the Bronze Age ( Chalcolithic). The concept has been mostl ...
jet went out of fashion until the early 3rd century AD in
Roman Britain
Roman Britain was the period in classical antiquity when large parts of the island of Great Britain were under occupation by the Roman Empire. The occupation lasted from AD 43 to AD 410. During that time, the territory conquered wa ...
. The
end of Roman Britain marked the end of jet's ancient popularity.
Early archaeologists (particularly Victorian) often failed to distinguish between jet and other jet-like materials
In particular in southern Britain the material described as jet was often
Kimmeridge Shale.
and some artifacts use more than one jet-like material.
For example the
Pen y Bonc necklace combines two or three jet pieces with other dark 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
Whitby is a seaside town, port and civil parish in the Scarborough borough of North Yorkshire, England. Situated on the east coast of Yorkshire at the mouth of the River Esk, Whitby has a maritime, mineral and tourist heritage. Its East Clif ...
itself,
rather it was transferred to
Eboracum
Eboracum () was a fort and later a city in the Roman province of Britannia. In its prime it was the largest town in northern Britain and a provincial capital. The site remained occupied after the decline of the Western Roman Empire and ultimat ...
(modern
York
York is a cathedral city with Roman origins, sited at the confluence of the rivers Ouse and Foss in North Yorkshire, England. It is the historic county town of Yorkshire. The city has many historic buildings and other structures, such as a ...
) where considerable evidence for jet production has been found.
[Ottaway, P., 2004, ''Roman York'', Tempus: Stroud ] The collection of jet at this time was based on
beachcombing rather than
quarrying
A quarry is a type of open-pit mine in which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some jurisdictions to reduce their envir ...
.
It was used in rings, hair pins, beads, bracelets, bangles, necklaces, and pendants,
many of which are visible in the
Yorkshire Museum
The Yorkshire Museum is a museum in York, England. It was opened in 1830, and has five permanent collections, covering biology, geology, archaeology, numismatics and astronomy.
History
The museum was founded by the Yorkshire Philosophical Soc ...
. Jet rings tended to follow the styles of existing metal rings although there were exceptions.
Jet pendants were carved cameo style with
Medusa
In Greek mythology, Medusa (; Ancient Greek: Μέδουσα "guardian, protectress"), also called Gorgo, was one of the three monstrous Gorgons, generally described as winged human females with living venomous snakes in place of hair. Those ...
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
Eboracum () was a fort and later a city in the Roman province of Britannia. In its prime it was the largest town in northern Britain and a provincial capital. The site remained occupied after the decline of the Western Roman Empire and ultimat ...
-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.
![Jet Oval Medusa pendant YORYM H2443](https://upload.wikimedia.org/wikipedia/commons/d/df/Jet_Oval_Medusa_pendant_YORYM_H2443.jpg)
In the Roman period it saw 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
The Evil Eye ( grc, ὀφθαλμὸς βάσκανος; grc-koi, ὀφθαλμὸς πονηρός; el, (κακό) μάτι; he, עַיִן הָרָע, ; Romanian: ''Deochi''; it, malocchio; es, mal de ojo; pt, mau-olhado, olho gordo; ar ...
.
Pliny the Elder
Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic ' ...
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
Aelius Galenus or Claudius Galenus ( el, Κλαύδιος Γαληνός; September 129 – c. AD 216), often Anglicized as Galen () or Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Considered to be one ...
.
Viking use
Vikings made some use of jet including rings and miniature sculptures of animals with snakes being a prominent theme.
The source of the jet hasn't been confirmed although Whitby is the most likely possibility.
Medieval
![PXL_20221128_123656073](https://upload.wikimedia.org/wikipedia/commons/e/e1/PXL_20221128_123656073.jpg)
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
Labour or labor may refer to:
* Childbirth, the delivery of a baby
* Labour (human activity), or work
** Manual labour, physical work
** Wage labour, a socioeconomic relationship between a worker and an employer
** Organized labour and the labour ...
.
A jet bowl held in the
Museum of London
The Museum of London is a museum in London, covering the history of the UK's capital city from prehistoric to modern times. It was formed in 1976 by amalgamating collections previously held by the City Corporation at the Guildhall Museum (fou ...
may have been designed to allow for this.
Victorian use
![Schwarzer Trauerschmuck2](https://upload.wikimedia.org/wikipedia/commons/c/c6/Schwarzer_Trauerschmuck2.jpg)
Jet as a gemstone became fashionable during the reign of
Queen Victoria
Victoria (Alexandrina Victoria; 24 May 1819 – 22 January 1901) was Queen of the United Kingdom of Great Britain and Ireland from 20 June 1837 until her death in 1901. Her reign of 63 years and 216 days was longer than that of any previo ...
.
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
Princess Victoria of Saxe-Coburg and Gotha (Victoria Franziska Antonia Juliane Luise, Victoire Francoise Antoinette Julianne Louise); 14 February 1822 – 10 November 1857) was the daughter of Ferdinand, Prince of Saxe-Coburg and Gotha-Koh� ...
.
Later the Queen wore Whitby jet as part of her
mourning dress
Mourning is the expression of an experience that is the consequence of an event in life involving loss, causing grief, occurring as a result of someone's death, specifically someone who was loved although loss from death is not exclusively ...
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. From above 1000 workers in the trade Whitby was down to 300 by 1884. 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. 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. Making tourist trinkets kept a few jewellers in work but by the end of World War II only 3 remained and the industry died out completely with their deaths.
20th century
In Whitby the Victorian tradition continued up until the aftermath of World War II. Jet Jewellery (both vintage and new) was then to remain out of fashion until the late 70s. In the 80s there was a fashion for Jet beads and antique jet jewellery started to rise in value. New jewellers took up the production of Jet Jewellery.
Jet substitutes
Glass was used as a jet substitute during the peak of jet's popularity. When it was used in this way it was known as French jet or Vauxhall glass. Ebonite
Ebonite is a brand name for a material generically known as hard rubber, and is obtained via vulcanizing natural rubber for prolonged periods. Ebonite may contain from 25% to 80% sulfur and linseed oil. Its name comes from its intended use as a ...
was also used as a jet substitute and initially looks very similar to jet, but it fades over time. In some cases jet offcuts were mixed with glue and molded into jewelry.
Anthracite (hard coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when ...
) 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
Unlike black glass
Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...
, which is cool to the touch, jet is not cool, due to its lower thermal conductivity
The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa.
Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...
. When rubbed against unglazed porcelain, true jet will leave a brown streak, although bog oak
Bog-wood (also spelled bogwood or bog wood), also known as abonos and, especially amongst pipe smokers, as morta, is a material from trees that have been buried in peat bogs and preserved from decay by the acidic and anaerobic bog conditions, some ...
, vulcanite
Vulcanite is a rare copper telluride mineral. The mineral has a metallic luster, and has a green or bronze-yellow tint. It has a hardness between 1 and 2 on the Mohs scale (between talc and gypsum). Its crystal structure is orthorhombic.
Vulcanit ...
and lignite will do the same.
When non destructive testing is required X-ray fluorescence spectroscopy
X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis ...
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
Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolysed ...
. No other black "gemstone" behaves like this.
See also
*Petrified wood
Petrified wood, also known as petrified tree (from Ancient Greek meaning 'rock' or 'stone'; literally 'wood turned into stone'), is the name given to a special type of '' fossilized wood'', the fossilized remains of terrestrial vegetation. ' ...
*Oltu stone
Oltu stone ( tr, Oltu taşı) is a kind of jet (lignite), jet found in the region around Oltu town within Erzurum Province, eastern Turkey. The organic substance is used as semi-precious gemstone in manufacturing jewellery.
Location and extracti ...
References
External links
Gemstone Guide: Jet
Roman Objects in the Yorkshire Museum
{{DEFAULTSORT:Jet (Lignite)
Coal
Organic gemstones
Sedimentology
jet