Then over at Fairy Dust Teaching (one of my first and favorite frequented blogs!), they started popping up a lot. Sally first mentioned them from another site called Red Bird Crafts:
Which gave her the idea to make birthday rocks and letter rocks using stickers as well:
As you can see, the ways to make them and their uses are both limitless! I hope you enjoy making rocks with and/or for your little ones this summer! I'll post mine when my boys and I make ours. Thanks to Red Bird Crafts and Fairy Dust Teaching for the inspiration!