Well the Artaunon stone is a very special quartzite, located in the German mountains called Taunus - hence the name (the name Artaunon appears in an old roman description of an ancient celtic city, so-called "Oppidum", which was nearby the quarry). The stones have been already used in older times as whetstones. But due to their hardness it is very difficult to cut an lap them. Hardness is around 7-7.5 according to Mohs, which is only little less than carborundum (9) or diamond (10). The stones consist of more than 80 % of very fine quartz particles that are embedded in the stone matrix like a sandstone. So it is not pure quartz but a so-called quartzitic sandstone.
With surry the stones are very fast. Slurry can only be raised effectively with a DMT. Diluting the slurry during progression, the edge gets shave ready within minutes. I love the edge these stone gives, very fine and sharp but also smooth. The edge gets even finer when the last strokes will be done with oil or you can get a very special "taste" of the edge, if you use a thuringian slurry stone to raise a thin thuri-slurry on the Artaunon for the last few strokes.