Strata
Initial Release
In version 4.80 Hardcore Stratification was added. It works by dividing the stone beneath the overworld into different layers, or "strata". These layers then require different qualities of picks in order to be able to mine them. Note that the picks required to mine various ores are not affected by this change, even though their visual appearance will match that of the surrounding stone, and they may take longer to mine at depths. In other words, the same tools in vanilla and the mattock may be used to mine the various ores regardless of the strata in which they appear, so even if you descend to a depth where you can no longer mine the stone, you may still be able to mine the ores it contains. This was done to further promote caving as the mining method of choice in the early game. And then in version 4.85 it was changed so that if you were to mine a strata block it would drop its vanilla equivalent, unless you used a silk touch. In which case you would obtain the stratafied block.
World Effects After and Before Install
If you uninstall Better Than Wolves, all strata blocks in your world will automatically revert to their vanilla equivalents. Also note that at present, worlds previously generated do not automatically stratify, and thus there will be underground (and thus largely invisible) "seams" in your worlds that you may run into while mining.
