This piece was created using Roman glass beads, fixed in place with a knotting process.  The necklace is attached to a patinaed brass pendant with an etched Equal Armed Cross on it. 
 
Dating back from the first century or earlier Roman glass was made on a very large scale. Artists and buyers love it because of its beauty and age.  Most of it is found in excavation sites around Israel. Exposing the glass to different metals or chemicals during the creation process tinted it. It can also develop a patina as it ages.
Much of the signature color, as mentioned above, occurred through centuries of chemical reactions, which unfortunately means that it's easily damaged. This glass can be damaged by chemical exposure, including our natural body oils. Keep household chemicals away from this glass, including hairspray and other aerosols, liquids including water.