The chao like to play with Chris very much. They want to make him happy, so they decided to give him the shiny rock that many people tried to take from them before.
Chris isn't sure if the very shiny rock is safe to touch, since it sparkles so much without an obvious light source.
Eggman never discussed about the chaos emeralds with his son, worried he would try to gain one for him, crossing paths with Sonic on the way