Rocks in a bag

You know the saying it feels like you are carrying rocks in your bag? Well today I found out it is true. My darling little girl who happens to love rocks has decided to weigh her bag down with a ton of them. I have been noticing lately that when I carry amber's backpack for her that it weighs a ton. Plus she had so much crap in there that it was hard to get her binder in at times. So she came home from her dad's this evening and I decided to go through it. She had about 5 lbs or so of rocks in one of the pockets. I cant believe the kid has been lugging that around for so long. I guess a couple weeks ago she picked them all up at her grandma's. Now I am trying to figure out what she was thinking and why she would carry that around for so long. I guess I need to check her bag more often