Here's a handy tip that will give them natural grit and also give them a jump start on forming immunity to the coccidia and other microbial life in your soils...give them a shovelful of your local earth, grass and all. They will climb on it, pick at it and eat from it. More helpful even if the soil comes from near where your other chickens live. Chicks brooded by an actual mama will gain these from their mother, but brooder raised chicks don't have that opportunity when their immune system is the most active~first two weeks~ in forming antibodies. Then folks put them out on those soils at the age of 2 mo. and they wonder why they get coccidiosis and die.
I do that when I can, however this time of year my local soil is frozen into a solid mass (like granite but harder) from the surface to 6 feet down. It would take dynamite to get a shovelful!!

But I have to add granite chips to my sand it is so fine it has virtually no rocks for grit.