I suspect you would be helped by viewing the excellent collections shown online by the Picards:

http://www.picardbeads.com

However, please be aware that questions such as "How old is this bead" can be difficult to answer. Many beads were made in ongoing editions, and might span decades.

Your bead is a Venetian millefiori bead. It would have been made after ca. 1825, and as late as ca. 1950.

Jamey