Emerald is the most precious stone in the beryl group. The name comes from the old French word esmeralde, which was derived from the Greek word smaragdos meaning green stone. By definition, emerald is any medium to dark green beryl colored by chromium. Green beryl colored only by vanadium is not considered to be true emerald, but rather as simply green beryl. Since the 1960s, the American jewelry industry changed the definition to include vanadium colored beryl as emerald, but in the UK and Europe, they are still not recognized as such.