whetstone– a sharpening stone used to sharpen the edge of metal tools and weapons (such as knives, scissors, and scythes). Sharpening stones come in a variety of sizes and shapes.
The Pike Manufacturing Company, of Haverhill New Hampshire, had the largest whetstone business in the world, until the 1920's and 1930's when artificial abrasives took over the market and the business was moved to Littleton, NH. Their whetstones were made from a mica schist, and there are some myths and legends associated with the “Indian Pond” whetstones.
Grafton County, New Hampshire was especially noted for the presence of Novaculite–siliceous rocks valuable as whetstones.
-Photograph of an old-fashioned Whetstone Wheel-