Stone blade fabrication allows you to make stone blades out of slate. Once learned, you may use the menu option "Special/Forge a stone blade" to turn two slate into one stone blade.
This skill has seven levels. At lower levels, there is a chance that you will fail every time you attempt to make a blade. When you fail, you will either break two slate (with no other effect) or one slate (causing your skill to go up by one level). At level 7, you will always succeed.