Hybrid I could not even venture a guess at dating your piece. This needs a hands on inspection by someone who deals in antique jewelry, the popularity of Victorian stone , pebble or agate jewelry was encouraged by Queen Victoria and it began as a souvenir of her trips to Scotland. From the mid-1800s Queen Victoria frequented Scotland and her Scottish castle, Balmoral. By the later 1800s it was being made in England and Germany as well. It was introduced in Paris in 1855. Scottish jewelery was popular in England until around 1861.