a name given by our artificers to a kind of stone, which they use for setting an edge upon knives, chisels, and other tools. It is a greyish coloured stone, containing a large quantity of talc-y particles, and splits easily into thin flakes. It is a soft stone, and used only to finish the setting an instrument after the edge has been prepared by grinding or rubbing the tool upon some other stone of a coarser texture. We have this from Newcastle, and many other parts in the north of England, where there are large rocks of it in the hills.