Rock Id

[Angelfin]

My kids picked these up for me to put in my tank ,while we were camping in Southern Indian , my daughter called the round ones meatballs, I think that are geodes, I don't want to break them because I like them round, I like that my daughter called them meatballs, they all found in streams and a couple were found in a cave floor. Do you think these will be safe and how would I test them?