Chicks in the yard.

Hi everyone,
So I have four day old chicks and would love to treat them with the occasional fresh veggie. I have called everyone in the Denver metro area and I can't find chick grit. I do live on a mountain made of granite. Our soil really isn't soil its more like sand. I read in another thread you can take the dirt from your yard and use it for chick grit but I'm afraid they might eat a piece of sand that is too big. Is that a possibility or am I being a crazy chick momma? Thanks in advance.
pepperfan.