The Belgian whetstone is often compared to a 4000 - 8000 grit whetstone, using the Japanese grit system, but it must be borne in mind that it is a  natural product, and therefore no stone is 100% identical to another. The grit rating is given purely for information, and tells you little about the specific characteristics of the stone. The advantage compared to other whetstones is: A Beglian whetstone sharpens very finely and very quickly. No other whetstone possesses this combination.

The hardness of the garnets ensures that they are able to hone any kind of steel, including stainless steel (inter alia, 18/8 and 18/10 stainless), Damascus Steel and HSS High Speed Steel.

The geometric shape of the garnets gives the whetstone another unique characteristic. The smooth shape of the garnets means that they sharpen the metal without leaving behind tiny burrs.  This results in a fine gleam without scratches on the blade, which makes the knife considerably easier to use.

A few examples:

1. A razor sharpened with a Belgian whetstone does not damage the skin during shaving. The garnets do not leave any tiny burrs on the blade, which is unique to the whetstones!  This means that there is no chance of skin irritation! The Belgian whetstone gives a razor-sharp blade and unrivalled comfort during shaving. Without skin irritation, the skin feels very soft after shaving.

2. Kitchen knives, hunting and pocket-knives keep their sharp blade for a long time, and can be made razor sharp in the twinkling of an eye.

3. The blade of all kinds of tools such as chisels, gouges and axes is polished so finely that materials like wood fibres are cut through quickly and cleanly, resulting in a smooth finish. There are no nicks in the surface. This is why the stone is sought after by carpenters and sculptors.

Various fields of application of the Belgian whetstones range from razor blades, all kinds of cook's and kitchen knives, hunting and pocket knives to chopping and cutting tools.

Naturally formed stones with a Coticule/BBW combination do occur sporadically. The Coticule layer remains attached by nature to the BBW layer. These rare whetstones can be used on both sides: preliminary sharpening on the BBW side and fine honing with the Coticule side. These stones can be recognised by the non-rectilinear transition between the Coticule layer and the BBW layer. 

Differences in Coticule layers

The different Coticule layers that can be exploited are exposed to various environmental factors during their formation. This results in the hardness and composition of the Coticule seams differing from each other. A harder Coticule is more suitable for sharpening of woodworking tools. The likelihood of cutting into the Coticule is very small. 

A softer Coticule has the advantage of releasing its garnets very quickly, thus creating a grinding compound. This property is particularly appreciated by razor users. If you would like to learn more about the characteristics of the different Coticule-layers we advice you read following article written by Henk Bos.
 

Link 

A wide variety of sizes

Coticule whetstones are produced both in rectangular and non-rectangular shapes (known as Bout de Coticule). We endeavour to achieve as many rectangular stones as possible, but due to a whim of nature, only a limited number of stones are suitable. Stones longer than 15 cm and wider than 4 cm are the exception rather than the rule. Fortunately, in many cases, the dimensions mentioned are sufficient to sharpen a wide range of knives.

Belgian Blue Whetstone (BBW)

The Belgian Blue Whetstone, or BBW for short, is extracted together with and at the same location as the Coticule. The BBW comes in wide vertical strata with the thin Coticule seams in between. The BBW was formed in the same way and at the same time as the Coticule. The presence of iron oxide in the stone explains the bluish purple colour. Just like the Coticule, the extraction of the BBW is a time-consuming task that must be carried out very meticulously, without the use of machinery.

The Belgian Blue Whetstone consists of 1 layer with a thickness of between 13 and 16 mm. The BBW, unlike the Coticule, comes without a substrate to give it extra strength. The BBW is not divided into categories like the Coticule, and there are almost never any blemishes in the surface. The Belgian Blue Whetstone is only produced in rectangular shape and due to the deposition of thick strata of sedimentary rock, large sizes are the rule rather than the exception. Production is carried out using traditional methods, and a small tolerance as regards dimensions is perfectly normal.

Whetstones in different shapes

We produce a comprehensive range of BBW whetstones with the suitable profile for sharpening various cutting tools. The profile of the whetstones can easily be adapted to your wishes easily by making use of the softness of the stone.

BBW Slipstone: For round chisels and gouges. A BBW slipstone measures 100x40 mm and on the two long sides, the edge is rounded. Available in 3 curve combinations, with diameters 6/2 mm, 10/3 mm and 13/3 mm.

BBW V-stone: for V-shaped chisels and gouges. A BBW V-stone measures 100x40 mm and has angles on the two long sides, 1 with an angle of 45° and the other with an angle of 70°.

BBW Multiform: for round and V-shaped chisels and gouges. The BBW Multiform is available in 2 sizes: 100x40 mm and 150x50 mm. The slanting side has an angle of 45° and the curve diameter of the curved side increases from2 mm to 13 mm over the length of the stone.