Quote Originally Posted by onimaru55 View Post
Any example of limestone hones for razors ? I've never seen one.

Poor choice on my part... Thinking back when I was a kid and we would sharpen our pen knives on pieces of limestone that was common in our neighborhood, or even sharpen on a concrete sidewalk. The point I was trying to make was that natural stones be they limestone, silicates, or whatever, usually yield an abrasive particle distribution that is very wide. The useful coticules are unique in that they naturally yield a reasonably tight abrasive particle size distribution.