whet slate 砥石
Whet \Whet\, n.
1. The act of whetting.
2. That which whets or sharpens; esp., an appetizer. ``Sips,
drams, and whets.'' --Spectator.
{Whet slate} (Min.), a variety of slate used for sharpening
cutting instruments; novaculite; -- called also {whetstone
slate}, and {oilstone}.