Djed pillars were among the amulets most commonly placed on mummies. They were used to represent the abstract concept of stability. The pillars were also associated with the god Osiris and were said to represent his backbone. The spell in the Book of the Dead associated with them calls out to the god: 'Raise yourself up Osiris! You have your backbone once more. O weary-hearted One; you have your vertebrae!' Gold was sometimes used to make djed pillar amulets since it did not tarnish and could endure for eternity, but it was expensive. Turquoise, lapis lazuli and blue faience were more commonly used as green and blue were associated with regeneration.