Aviary grit for chickens

[Cyclingchix]

Went to my local feed store and all they had was aviary grit. I was told by one of the workers who is raising 200 chicks that aviary grit is okay to feed 6 week old chicks. Anyone ever use aviary grit for chickens?

 

[Yay Chicks!]

I think that I read that it has calcium in it, which would not be good for 6 week old chicks...