Translucent arkansas is the hardest stone (as far as I know, with Llyn idwal) and Thuringians are the softest (and the aoto I have). CF are hard, the same goes for the Grecian hones. They look like natural UK hones, I don't know what they might be. If they are 16k+ estimated grit, I don't know any other so fine finisher from England. They kind of look like WOA, but I don't think they are. An old test is to try scratching them with a copper wire (not coins), if nothing happens to the stone, it is CF or LI. If they get scratched, they are something else.