The Moonstone is a blue spherical jewel which is featured in the movie, Tinker Bell and the Lost Treasure.
The Moonstone was always placed in the Scepter, for each eight years on full blue moon so Pixie Hollow would receive blue Pixie Dust, that was used to help the Pixie Hollow Tree. Tinkerbell was chosen to make that year's scepter, and took the Moonstone home with her. As she was working on the scepter, she accidentally broke the Moonstone. In despair Tinkerbell went to an island due north of Neverland, to search for the Mirror of Incanta, which granted three wishes, but two were spent, as then only one wish was left.
Tinkerbell wanted to restore the gem to its spherical form, but accidentally wished for Blaze to be quiet. After no luck, her only hope was to make its shape different, and so, with Terence's help, they made a new shape.
By using all the pieces, along with a diamond Tinkerbell had found, they designed the scepter so that when the blue moon shined through the diamond, it refracted the light into the moonstone pieces, maximizing the effect, and creating more blue pixie dust than ever had been seen at any prior Autumn Revelries.