Medium hard formation with high compressive strength. Such as hard shale, limestone, sandstone, dolomite, anhydrite and marble.
高抗压强度的中硬地层，如硬页岩。石灰岩。砂岩。白云岩。和硬石膏。大理石。
2
Cementation is showed by the secondary enlargement of quartz and feldspar, the successive formation and pores filling of cementing material of authigenic clay mineral, calcite and anhydrite, etc.