... below: Hot-Pressed Diamond Drill Bit matrix and Rock Formation Comparison FormEarth PropertyRockBit Matrix TypeSoftShale, soft sand, peat, mudstone, marl, etcFlat Bottomed Type ... Rocks, Mixed Pegmatite, Biotite Granite, Plagioclase Diorite, Mixed Gnesiss, Tuff, Rock and other mixed Light Particles.930-32, 33-35Carbide Powder Mixed ...