May

Emerald is the traditional birthstone for May, but there are several alternative stones associated with this month.

Agate, a type of chalcedony, is the top alternative and has been a birthstone since Roman times. It is also associated with the star sign Gemini.

Chalcedony is a birthstone alternative for May. It comes in various colors based on the minerals in it. Named after a town in Asia Minor, it was known to the ancient Greeks and Romans.

Carnelian is a type of quartz that is mostly associated as a birthstone for August but in the Hebrew calendar is associated with May alongside agate and chalcedony. 

For May's birthstone, green is the traditional choice, making it an excellent gift option for your May-born loved one.