... Comparison FormEarth PropertyRockBit Matrix TypeSoftShale, soft sand, peat, mudstone, marl, etcFlat Bottomed Type, Arc-shaped Type, Steps Shaped Type(PDC coring or non-coring ... )MediumLimestone, marble, dolomite, rhyolite, limonite, etcSteps Shaped Type, Concentric Circles Type, Canine Tooth Shaped Type, Wheeling Gear Shaped TypeHardBasalt, gneiss, granodiorite, hornfels, pegmatite ...