Mohs hardness scale is for minerologists and people who use things made out of minerals. That is all of you road users, as roads are mostly rock (asphalt) or sand (concrete). Having bits harder then the road materials such as quartz (Moh 7) and feldspars (7) would cause for more rapid road wear. So steel (7) bits on heavy vehicles. For bikes go for the carbide. For a real show stopper use Topaz (8), Ruby ( 9 ), or Diamond (10).