Jet (lignite)

et is a type of lignite, a precursor to coal, and is a gemstone. Jet is not a mineral, but rather a mineraloid. It has an organic origin, being derived
from wood that has decayed 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.