Why.....

So, as I have posted many times, Lily likes to run. We took her to the playground yesterday to give her the opportunity to do so.
Chris and I were talking, and Lily was playing on the various equipment. I looked at her at one point and thought she looked like she was chewing. I ran over and asked her what she had in her mouth, while I grabbed her cheeks.
"I eating rocks."

WHY????? I do not know. I am sure it was less than a half teaspoon, but she did in fact pick up a small handful of crushed gray rock, put some in her mouth, and commence to chewing. I could hear the grinding noise as she had a couple in her teeth....she did spit them out when I asked her to, but seemed confused about why I would ask that of her.... Guess I will see a few of them shortly from the other end...
So odd....