About Emerald as Birthstone And Anniversary :-
As the birthstone for May, the emerald, a symbol of rebirth, is believed to grant the owner foresight, good fortune, and youth. Emerald, derived from the word “smaragdus,” means, quite literally, “green” in Greek.
Traditionally, gifts given for a 55th anniversary featured emeralds. Emeralds are precious stones, and they're relatively rare; their association with the 55th anniversary symbolises the immense value and precious rarity of such an incredible milestone.