It is the best natural stone in the world, Belgian Blue Coticule has a grain of 6000 and is composed of approximately 35 to 40% of small crystals of spessartine garnet which gives it this “razor” stone property.
This small slurry stone which measures 40 x 40 mm (1.5'' x 1.5'') is particularly useful for bringing out the dye (slurry) of another larger blue Coticule. You simply have to rub it circularly on the other stone and the mud will form in no time.