Amethyst
Amethyst is a calming crystal that may help children sleep better and prevent nightmares. It's often popular with children because of its purple color. (8mm)
You can place a crystal underneath their pillow or by the bed, and make up a ‘Magic Spray’ for younger children. Simply fill a bottle with water and a few drops of lavender essential oil, and add an Amethyst crystal in too. Spray this around the room just as they are going to bed. Cleared and blessed before shipping.