Inclusion 1

An inclusion is any material or particles in the stone that is not what the majority of the stone is comprised of.  It’s like having a weed in the middle of your lawn. These inclusions can be softer than the surrounding stone, or harder. A harder inclusion is almost always ‘toxic’ in the sense that it will disrupt the sharpening effort and/or harm the blade. Softer inclusions can usually be considered viewed as being safe to hone on. However – those softer minerals can disrupt the honing feedback. 

The photo up above shows a typical inclusion; it appears to be made up of the same material as the Suji and Renge in that stone, along with a couple of other minerals. In a general sense, this one was safe to work on. However, careful inspection of that area is an ongoing concern. The top edge of the pocket containing the reddish material can chip off easily. Usually, that would not be a problem with a heavy blade, like a Chef’s Knife. But even a small shard of stone can kill the edge on a straight razor quite easily. 

Sand eyes; these are nest pockets of Su that contain what appears to be sand grains. These grains are quartzite inclusions that will most definitely scratch the hell out of anything that they come in contact with, and I’ve yet to see any edge survive even a short time in contact with them. Unfortunately – I do not have a photos of this type of inclusion. In time, I’m certain that I will come across another stone with this issue and I’ll be sure to document it and post it here. Stay tuned. 

© Keith V Johnson 2014 - 2018