But he didn't crystalize. And it's not that sparkly. And why did Xion not have dark stuff surrounding her??
Repliku was made of the memories and darkness in Riku's heart. Xion was made of the memories of Sora's. Because of the darkness, Repliku had darkydeath, while Xion had none. As for the sparkles... I think they're almost always present in every death. And now the crystals... Didn't every organization member die sort of... by their own element? When Marluxia died, petals emnated from him. When Axel dies, fire come off of him. The crystals must be representing light.
EDIT: Actually... never mind. Just saw a post from before. Disregard that last part.