... Shaped TypeHardBasalt, gneiss, granodiorite, hornfels, pegmatite, etcSolid HardHard granite, quartzite, hard slate, chert, basalt, etcHot-Pressed Diamond Drill Bit Hardness ... , Feldspar Pegmatite, Amphibolite Rocks, Felsic Migmatitic Amphibolite, Anorthosite, Granite, Quartzite Siliceous Tuff Lava Gravel.115-8, 8-10, 10, 15 ... , 10-15, 22-25Quartz Chert, Chalcedony, Melting Tuff, Pure Quartzite, etc