Modern whetstones are made of a bonded ceramic abrasive. Silicon carbide or aluminum oxide ingredients are essential in the process. It is worth pointing out that bonded this way abrasives provide a faster cutting action than most natural stones
Roy Underhill would probably disagree with me. In his book The Wood Wright's Companion, he argues that stones found in a quarry or a mine can replace modern products on the market. Very possible that it is the case. I have no experience with natural stones yet.
One thing I know for sure – stones get out of shape. Since I first started the company, I used three sets of whetstones in total. Each stone is different than the other. It behaves the way it wants, depending on the bonding compound used. Cheaper stones start to lose their material while knife sharpening and can cause minor damage.
Knives and scissors can be hard to get sharpened. Curved knives, for example, cannot be sharpened on a whetstone due to their shape. The same thing with serrated knives they will ruin your stones leaving marks on a perfectly flat surface. For this case, I have a good set of electric grinders.
Thankfully curved knives are not in every kitchen.
Speaking of the flat stones (not the Earth), in my experience, flattering tools never found their use in my inventory. When I work with a new whetstone, I work from the center of the stone out, giving it the V shape. This shape helps me to be more precise with the angles that I give to each knife. Knives can be separated into groups by their cutting-edge angle. We will talk about it in future articles.
Eventually, you need to work with your stone. Each of your movements gives a new shape to it. Once you learn how to focus on areas on the stone's surface, you will understand how to shape your stone the way you want and that works best for you.
Regarding the grit number, I prefer a set of whetstones in the range of one to six thousand grit. In collaboration with the electrical grinders, I get the best result in return. I tried to go higher than six thousand, but it feels like the difference is not significant. I leave the window open in case I find a good enough reason.
It is more about your style that you find attractive. It all comes with experience, just like everything else.
We specifically work with kitchen knives (serrated or straight blades) and fabric/kitchen shears. We DO NOT sharpen swords, ceramic knives, curvy knives (karambit type), all blades without a handle, straight razors, garden tools.