STOW May Birthstone Charm (Green Onyx)Green onyx is the birthstone for anyone born in May. This precious stone is said to be a symbol of purity and restfulness. Many say it has the power to reduce stress, worries and fears. Adding a birthstone to your locket is a wonderful way to signify your own birthday or those of your loved ones. As all of our birthstones are made from natural semi precious stones each one is special and unique, just like the wearer.