The Covenant stone works best after a quick soaking in water. The small slurry stone provided with each sharpener is used to build up a lay of “mud” on the surface of the hone. The combination then polishes a very smooth keen edge on any quality blade.
In the days before synthetic abrasives, virtually every corner of the globe depended on a locally quarried stone for their sharpening needs. Any mineral harder than the steel will eventually generate an edge on a blade, but not all stones are created equal. The ideal natural stone is made up of microscopic, sharp-edged crystals or fragments bound together in a stable matrix of even finer material. Each fragment actually cuts extremely fine shavings of steel off the edge as the blade passes over them.
Over the centuries, the mineral deposits of certain areas have become more famous than others for producing high quality sharpening stones. Practically every American has heard of the novaculite stones from Arkansas. Those more into sharpening might recommend the Belgium blue and coticule hones, Finnish Wastilas, German Thuringians, Slovakian Rozutecs, Norwegian slate stones, or the Turkish version of novaculite. Even more renowned are the incredibly complicated varieties of natural Japanese waterstones and the similar hones quarried in China.
Given it is normally accepted that iron was first worked into tools and weapons someplace in the Middle East, it should probably not come as a surprise that there is also a native sharpening stone in this area. Israeli custom knifemaker Tslil Censor explores the desert in search of sources for this stone, which he then hand quarries, cuts, laps, shapes and polishes into a limited number of very special hones. He calls his handmade sharpeners “Covenant Stones” and each is appropriately boxed in acacia wood.