Belgian Blue Stone Medium Fine ~ 8x3x.7"

Natural schist sharpening stones from the Ardennes region of Belgium used only with water for sharpening tools and knives that benefit from a fine finish and often as a pre-polisher for razors.

Belgian Blue and it's typically finer yellow 'Coticule' cousin were formed from clay and volcanic ash in a high pressure metamorphosis over 400 million years ago. As the rock was altered in the pressure and heat of metamorphosis 12 sided (dodecahedron) garnets formed in veins of mica; in the Belgian Blue stones roughly 30% of the stone is garnet. The blue color of the Belgian Blue is due to the presence of iron oxide in the stone. 

Garnets are quite hard and will cut a huge variety of steels, way more than many other softer silica based abrasive natural stones. In addition these garnets are not friable, that is they do not break down during sharpening, for this reason the technique used during sharpening is key. Belgian Blue garnets are 10-15 microns in size (approx. 800-1200 in Japanese grit scale) but tend to leave shallow cuts several microns deep (approx. 4-8K in Japanese grit scale) due to the small angles on the sides of the 12 sided garnets.

With a thick slurry rich in free rolling garnets used with a good amount of pressure (average pressure for synthetic stones) there are more abrasive particles that can cut a bit deeper making for a good amount of light metal removal. By adding water and reducing pressure there are less garnets to cut as deeply and the scratches become shallower to the finest possible finish which is obtained with a very light pressure and only water (no slurry) cutting with the embedded garnets only. 

This stone typically provides finishes analogous to a 3-4000 grit Japanese stone but can provide a much finer finish. It should be noted the scratches are different than natural Japanese stones, they are a bit deeper. For those familiar with Japanese natural stones it's tempting to compare to a hard/fine Aoto stone but the Belgian is quite different. It honestly took me some time to learn to get started on Belgians after working solely with Japanese.

8"x 3"x .7" | 220 x 80 x 18mm