Jet (gemstone)
mineraloid and minor 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.
The English noun jet derives from the French word for the same material, jaiet (modern French jais), ultimately referring to the ancient town of Gagae. Jet is either black or dark brown, but may contain pyrite inclusions which are of brassy colour and metallic lustre. 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. 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.
The public source identifies “Jet (gemstone)” as mineraloid and minor gemstone. This brief keeps that definition visible, then builds a research path around gemstone, mineraloid and minor.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Aug 5, 2026. The linked authority identifier is Q543694. The Library of Congress control number is sh85070150. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “Jet (gemstone)” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.