If anyone knows if I can put to my Iguanas chicken`s eggshell for more calcium!

Ground eggshells are great for most meat eaters or omnivores but since it's a animal product I would be leary to use it with a green iguana.
If you use it for another species be sure to grind it up after boiling the egg. For iguana's I can't recommend iguana dust enough for a natural whole food, specie specific supplement.