Although stones are mined in many places all around the world to be used as sharpening stones, there are great differences in the way they work. Each type of stone has a different composition. Even amongst sharpening stones from the same mountains you can often find clear contrasts. Factors that play an important role in the proper functioning of a natural sharpening stone are the grain size, the shape of the grains and the way they are bound together.
Where are natural stones mined?
There are a couple of mountains known for the mining of natural stones (which, of course, still need to be cut to size and flattened). Two important natural stone sources are the Belgian Ardennes and the American Ouachita Mountains in Arkansas. In addition, in the French-Spanish Pyrenees and the Dolomites (Italy) you can find usable natural stones.
The Arkansas stones are comprised of novaculite, a material which can only be found in these mountains. The grain density which leads to a very hard, waterproof stone is of great importance here. Depending on the part of the mountain range where they are mined, Arkansas stones are available with a relatively low grain size (approximately 400 to 600), but also with a very high grain size (approximately grain 10,000).
Arkansas stones are oil stones
The sharpening stones from the Ouachita Mountains are best used in combination with oil. It is because of the extreme grain density. The oil removes the sharpening residue more easily and leaves you with less resistance while sharpening. The main advantage of oil stones, compared to water stones, is that they don't wear out as fast. They often last for years. The disadvantage is the hardness which ensures that sharpening takes a relatively long time because the stones remove little material.
Belgian chunks from the Ardennes
Coticule whetstones, formerly known as Belgian Chunks come from the Ardennes. The grain size of these sharpening stones is difficult to determine. The remarkable thing here is that you can determine the coarseness of the stone yourself. The thicker the slurry you create, the lower the grain size (which varies between 1000 and 16,000). Adding a lot of water naturally leads to a thinner slurry and therefore a more polishing effect.
Another tip to get a finer 'grain' is to use talcum powder instead of water. The smoothness of the edge is also largely determined by the amount of pressure applied when sharpening. The less pressure, the flatter and therefore sharper the edge.
