Koru can also refer to bone carvings. Those generally take the shape of the uncurling fern plant. When bone is worn on the skin, it changes colour as oil is absorbed. The Māori took this to symbolise that the spirit of the person was inhabiting the pendant. When someone gives a pendant to someone else, it is the custom that they wear it for a time so that part of their spirit is given as well.
The koru is used in a stylised form as the logo of Air New Zealand and as an iconic symbol of New Zealand flora. Friedensreich Hundertwasser based his Koru Flag for New Zealand on the symbol, and it also formed the basis for a notable series of artworks by Gordon Walters. The koru is also the current symbol for peace in Japan.