Both Belgian Blue and Vielsalm Coticule are ancient stone layers found in the Belgian Ardenne Mountains with characteristics similar to both Novaculite and Siliciclastic sedimentary stone in that it is a metamorphic stone consisting of both gray and yellow volcanic ash mixed with tiny Spessartite Garnet crystals suspended in a clay matrix. However, due to its geology, both types of stone occur only in vertical seams sandwiched between two thick layers of bluish-purple slate and thus, they must be meticulously extracted mostly by hand. However, this type of extraction process is both very time-consuming and very labor-intensive and, quarrymen can only extract the stone for a few months each year due to inclement weather conditions. Consequently, both Belgium Blue and Coticule whetstones tend to be somewhat expensive.
Ceramic whetstones are meant to be used without water or oil, which means they can be used almost anywhere and are ideal for chefs or cooks who have limited working spaces. They will give you a very sharp blade and as their surface is very hard they will maintain their flat surfaces over the long-term, but as they have a fine grit, they can break if you drop the stone.
As opposed to water whetstones that require you to pre-soak the stone, the Norton oil stone is pre-filled with oil to save time and eliminate the need to pre-soak it prior to use and the lubricant stays on the surface during sharpening.  The oil also prevents metal from bonding with the abrasive surface by flushing away dislodged abrasive and metal chips.
One of the most well-regarded natural whetstones is the yellow-gray "Belgian Coticule", which has been legendary for the edge it can give to blades since Roman times, and has been quarried for centuries from the Ardennes. The slightly coarser and more plentiful "Belgian Blue" whetstone is found naturally with the yellow coticule in adjacent strata; hence two-sided whetstones are available, with a naturally occurring seam between the yellow and blue layers. These are highly prized for their natural elegance and beauty, and for providing both a fast-cutting surface for establishing a bevel and a finer surface for refining it. This stone is considered one of the finest for sharpening straight razors.[citation needed]
You might not need to spend hundreds of pounds to get the best knife sharpener, but you do need to know what you're doing. Warner gave me a crash course in the technique. As a newbie to this method, it took a while to get used to (especially since Warner handed me a knife that had never previously been sharpened) but after half an hour's practice and a little encouragement, I got the hang of it. Here's what I learned...

Over the course of two days I re-sharpened nearly a dozen old blades, including removing the secondary bevel on an old stainless Ontario saber-grind Navy diver's knife, convexing the edge on flat ground 1095 Schrade 55 that also came with a secondary bevel, and fixing a broken tip on an old Kershaw folder. These stones made quick work of the Schrade and Kershaw. Both had completely new edge geometry within 30 minutes apiece. The Kershaw looked like-new, as if the tip had never broken. And the Schrade cut much better than it's secondary bevel would previously allow, regardless of how sharp I got it with a ceramic rod and strops. The Ontario took a little more work, as it had been abused a little the last time I'd held it, over 25 years ago and was as dull as a case knife - one of the reasons I decided to go ahead and do a full saber grind - well, a slightly convexed saber, I suppose would be more accurate. But within under an hour of using the two stones and a couple leather strops (one with black compound, another with green), the Ontario was shaving sharp again too.

This is my first time ordering from hayneedle, but you came thru with flying colors. I was so happy to see the delivery come so quick as stated. It was just as i hoped it would be, i now have my whetstone sharpening stone, to really get my kitchen knives as sharp as i can get them. This to me is the best way to sharpen a knife, it takes patience but the reward is worth it. Thanks Hayneedle you rock!!! Ray D.

For the common sharpening purpose, generally, people tend to use two phases. In the first phases, they use the coarse stone to shape the edges then jump to the finer stone. In application, these of the two phases can be extended with the grit stone in between. It might be varying in the number of grits or mesh in different types of sharpening stone.
The newly designed dual-sided combination whetstone from Fallkniven features a super fine white ceramic stone (0, 1 micron) with a grit of 1400 to 2000 and the dark grey ceramic stone is made of synthetic sapphires (1 micron) and has a grit of 800-1000. There is no need to add any oil or water, just lay the blade on the stone, raise the blade's spine and deburr your blade on the grey side until it has a razor-sharp edge and then use the smooth white side to get a nice polished edge.
Diamond plates are available in various plate sizes (from credit card to bench plate size) and grades of grit. A coarser grit is used to remove larger amounts of metal more rapidly, such as when forming an edge or restoring a damaged edge. A finer grit is used to remove the scratches of larger grits and to refine an edge. There are two-sided plates with each side coated with a different grit.[14]