These amulets were made out of turquoise feldspar[1] or Egyptian faience, as is indicated in the Book of the Dead.
[1] In Ancient Egyptian, the word wadj means "green," though it is also known to refer to health and to flourish in life.
[2] The amulets have been dated to the Late Period of Egypt, specifically between the 26th and 30th dynasties (664–332 BC).
[4] Spells from the Book of the Dead state that if a wadj amulet is found intact, the wearer is healthy in the afterlife.
One held at the Museum of Fine Arts, Boston was found at the Giza Plateau.