Also, I learned something I did not know from that link (if t'internet is to be believed)
A note about the olives. Use the best you can find. Don’t use pitted black olives as properly matured olives are too soft to have their stones removed mechanically, so they will almost certainly be green olives which have been dyed with ferrous glucomate (E151, a synthetic coal tar).
Also, I learned something I did not know from that link (if t'internet is to be believed)