Originally Posted by
Vasilis
Cretan stones have grades. After this one has been soaked in oil for so long it's not visible, and it's way easier to identify them before they get soaked in oil, but there are basically three grades.
The grade that looks white before it gets submerged in oil. It's soft, faster than the other two grades, and in the 4-6k approximate grit. It's also a somewhat rare find, a pure white stone. Then there is the type than when is extracted has a grey color, which is the most "abundant" type found, in the 8k grit, slower than the white type, but still faster than a soft Arkansas, and finally, and the most important for us razor guys, the blue type. It's hard and the slowest, finisher grade, like a translucent Arkansas stone, but still extremely fast for its grit. And that's a fact for Cretan stones; they are extremely fast stones, even compared to man made stones. That's why they are also prone to overhoning, so, do be careful.
To find out if your stone is a finisher or not, clean-flatten it and try it.