Naniwa does make a "ceramic" range. It is a thin piece, like a plate and mounted on a metal plate of that size.
a) hard like hell adn it cost more
b) i have used the 1000 grit also green color > I tried using it over a period of 10 times No joy for me and didn't develop any feeling for the stone. It is somewhere at the bottom of the stone stack
c)Being me, I still prefer the Super Stones series as being soft, it does give a feedback. Apart from ocasionally cutting into it and it dish faster ( being soft) it is still my main stone.
Stay sharp and hv fun..