What is "oilstones"

Usage examples of "oilstones".

Squires tossed pails of water over cookfires, while soldiers took out their oilstones to give their blades one last good lick.

Poll, my dear, there are two coarse and two very fine oilstones on the bottom shelf of the medicine chest.

For some time Jacob and Stephen Maturin had been talking about the pleasanter sides of their evening with Mr Wright as they sharpened their instruments on variety of hones and oilstones by the Argand light in the orlop.