Good stuff! I've noticed your other work and am really impressed. I'm sure it's a LOT different than turning other "stone" (aka Tru-Stone, etc). Care to share your methods? Suspect it's not on a wood lathe.
It is VERY different from turning Tru-Stone. The stone I'm using is harder than knife steel! One if the tests I use to determine hardness is a scratch test. First I use a penny, which usually leaves a streak of copper on the stone. Then I go to my pocket knife, which quite often leaves some metal on the stone!
I don't mind telling the general aspects . . . but I don't want to get into 'trade secrets'!
Diamond slab saw to get 1" x 1" x 4-7" pen blanks.
Diamond drills for the hole.
Diamond grinding wheels to make it round and polish it and square the ends.
It has taken me many years and trials and errors to get to the process I use now. But they sure are beautiful!