Photo of Jet Lignite in Processed & Rough Form
Jet Lignite is a mineral with a hardness of 3 out of 10 on the Mohs scale of mineral hardness [?]. These Amorphously structured gems are made of a variation of things, their full chemical compound being unknown.
Jet is an organic gem material composed of lignite, and is a bituminous coal which can be polished. It is compact, homogeneous, has a hard, glossy surface and black interior variety of fossilized lignite or coal.
It is an opaque black coalified fossilized drift wood from the coniferlike, 180 million years old 'Araucaria' or monkey puzzle tree that has been dried and fractured following death of the tree; thus causing some of its woody structure. This wood was subsequently transported downriver by floods, during which sand grains entered shrinkage cracks and fractures in the wood, before becoming waterlogged and sinking into the black mud of the seafloor.
Jet is so effectively fossilized (by carbon replacement) that a thin section can readily reveal precise structural details of the crushed original wood that was the source of this essentially Victorian organic gem material.
It has an amorphous crystal system, and has a color of black or dark brown, and is opaque, with conchoidal fracture.
It has a velvety waxy luster, sometimes with pyrite inclusions and, when rubbed, becomes electrically charged.
Much was found in England (Whitby, Yorkshire), but today it comes from Spain (Asturias), France (Aude Departement), the USA (Colorado, Utah's Henry Mountains, New Mexico), Russia, Poland, India, Turkey, China, Spain, Germany (Wurttemburg), and Cambodia. Of these deposits only the British and Spanish deposits have been worked commercially.
Jet is warm to the touch, light in weight, induces electricity when rubbed on wool or silk. It burns readily with a sooty blue flame.
Imitations are black tourmaline (schorl), black andradite (melanite), black zircon, albertite, Kimmeridge shale, bog oak, horn, lignite, shale, vulcanite a hardened rubber, black-dyed chalcedony is called black onyx.
Other jet imitations are made of glasses and obsidians. A type of black glass material is known as Paris jet. It can be distinguished from other black stone or material simulants by touching its surface with a heated needle, which releases an odor of coal, or when it is rubbed, it gives off a strong odor. Misnomerly called black amber or referred as black turquoise. Sometimes applied to a black marble. Also called scorpion stone, jet coal, gagate, agstein. Also spelled jett.
Jet is often confused with lignite, cannel coal, and shale.
The specific gravity [?] for Jet Lignite is 1.33, its refractive index [?] is 1.64-1.68, and its double refraction [?] is None.
History
Jets name is derived from Greeks and Roman word "gages," which is the name of a town and also a river Lycia in Asia Minor.
It is an ancient gemstone that man has used both as a talisman and a jewel for over four thousand years.
In old English, jet was called "geate" or "geat" and later became "jeat," and in Medieval times became "gette." In French, jaiet, jayet, jyet, jais, and in the past was called gest, getz. In German, Gagat and Augstein. In Spain, azabache, may be a Farsi name (an Iranian term for Azara- Padegan or Azar-Pad, where the eternal fire for Zarathustrian people was protected and also made fire from this coal-variety because the fire was relatively permanent.
Industrial Usages
Jet is worked on a lathe. It is used for mourning jewelry, rosaries, ornamental objects and cameos; used as carved and engraved articles as seal, beads, buttons, and finger ring or faceted. It was also used as a mirror in medieval times and is suitable for carving.
It is imitated by other types of coal (anthracite, cannel coal), glass, vulcanized rubber, and onyx.
Stones should be kept separate from harder material such as metal, etc., because they may scratch the jet. It may be washed in warm water mixed with soap and cleaned with a soft brush.
According to its toughness there are two varieties, hard and soft. Hard variety is tough and durable which can be carved and polished, retain its shape and luster for long time, and is named as plank jet. Soft variety is is so brittle that it tends to crack shortly after it has been worked or subjected to heat, and known as cored jet.
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