The Romans thought jet was…

.. magical, and they put it into amulets and pendants because of its supposed protective qualities and the ability to deflect the gaze of the “evil eye”.  Pliny the Elder of Rome wrote “the kindling of jet drives off snakes and relieves suffocation of the uterus.  Its fumes detect attempts to simulate a disabling illness or a state of virginity”.

Samples ahve been found all over the Roman British Empire and in Europe including bracelets made of jet with gold inserts found along the Rhine.

(Samples:  Modern Whitby jet jewelry despite advanced technology for cutting and inlays is expensive.  This necklace made of sterling and Jet sells for $500, and the ammonite shell inlays drive the price even higher.  Many past and current jewelry samples come from Scotland and represent Celtic symbols)