Here is a beaded necklace made up of faceted French jet beads and rock crystal spacers strung on white thread. The largest center bead measures 14mm and they graduate down to 5mm. The length of the necklace is 29" long and can be put over the head easily. The clasp is stamped 14K but I'm not sure if that is accurate.
French Jet & Rock Crystal Graduated Beaded Necklace