Most of them look like slate, which is fine for tanks, assuming it is free of herbicide and chemicals.
I'm not sure what the 2 white/ cream rocks are. Put some vinegar on them and see what happens. Maybe post some more pics of them showing the other side.
In future, you don't have to boil rocks for 2 hours to kill anything on them. Just wash them and put them in a bucket of water. Change the water every day for a couple of weeks. Then rinse them off and put in a pot of water and bring to the boil, then let them cool down. Then rinse off again and they should be fine to go in the tank.
However, any rock collected from the field could be contaminated with herbicide or other chemicals so it's a gamble using them.