There is no known name for a 55th wedding anniversary, though modern and traditional 55th wedding anniversary gifts have a theme of emerald. Some may call it the "Emerald Anniversary." Like emeralds, a marriage that lasts 55 years is a very rare find.
Some people use turquoise instead of emerald stones. Traditionally, the most important anniversaries are the fifth year, which signifies the end to the "newlywed" era, the 25th, which is the silver anniversary, and the 50th, which is the golden anniversary. The 60th wedding anniversary is known as the Diamond Anniversary because very few people reach that milestone.