I'm in Perth, Australia and not really seeing any product for sale called 'crushed granite' here. It's very very sandy here though, if they weren't in a box I can't see that as being a problem.
My daughter wants me to ask about wet chick feed... ? What is it I guess...?
If you have a lot of sandy soil with small pebbles, get a scoop of that and place it in the brooder for them to pick through.
Wet chick food - add a little water to your chick starter to make it into a "mash" - it should be about the consistency of prepared oatmeal.