Jet (gemstone)
Mineraloid and minor gemstone / From Wikipedia, the free encyclopedia
Dear Wikiwand AI, let's keep it short by simply answering these key questions:
Can you list the top facts and stats about Jet (lignite)?
Summarize this article for a 10 year old
SHOW ALL QUESTIONS
Jet is a type of lignite,[1] the lowest rank of coal, and is a gemstone. Unlike many gemstones, jet is not a mineral, but is rather a mineraloid.[2] It is derived from wood that has changed under extreme pressure.
Quick Facts General, Category ...
Jet | |
---|---|
General | |
Category | Mineraloid |
Formula (repeating unit) | Variable, but rich in carbon |
Identification | |
Color | Black, occasionally brown |
Cleavage | None |
Fracture | Conchoidal |
Tenacity | Brittle |
Mohs scale hardness | 2.5–4.0 |
Streak | Brown |
Specific gravity | 1.3–1.4 |
Optical properties | Isotropic |
Refractive index | 1.640–1.680 |
Dispersion | None; opaque |
Ultraviolet fluorescence | None |
Common impurities | Iron, sulfur |
References | [citation needed] |
Close
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.[3] Jet is either black or dark brown, but may contain pyrite inclusions[4] which are of brassy colour and metallic lustre. The adjective "jet-black", meaning as dark a black as possible, derives from this material.