.. at least 10,000 BC when a model of a botfly larva was found made of it near Baden-Wurttemberg, Germany. Britain used it through the Bronze Age, predominantly for necklace beads.
Jet went out of fashion until the early 3rd century AD, although the Anglo-Saxons and Vikings – and later those in the Medieval period used it sporadically. In Roman Britain from that point on it was used in rings, hair pins, beads bracelets, necklaces, and pendants, but it was not worked in Whitby itself. The raw goods were transferred to what is now York.
Samples of historical jet works have been found on the beaches mostly.
(Pictures: Modern day cutting Whitby is no easy task, and a recently carved jet cameo with pink sea shell)