A form of banded Chalcedony, Onyx has long been used for decorative and jewellery purposes.  The Romans in particular loved Onyx for carving seals and cameos.  The origin of the word onyx cames from the Greek 'onux' which means 'fingernail'.  According to ancient Greek legend, as the goddess Venus slept, her nails were clipped by Cupid and left scattered on the ground.  The fates turned the clippings to Onyx stone so that every part of the goddess would remain  immortal.