Whetstones and Oilstones
Whetstones may be natural or artificial stones. Artificial stones usually come in the form of a bonded abrasive composed of a ceramic such as silicon carbide (carborundum) or of aluminium oxide (corundum). Bonded abrasives provide a faster cutting action than natural stones. They are commonly available as a double-sided block with a coarse grit on one side and a fine grit on the other enabling one stone to satisfy the basic requirements of sharpening. Some shapes are designed for specific purposes such as sharpening scythes, drills or serrations.
When the block is intended for installation on a bench it is called a bench stone. Small, portable stones (commonly made of bonded abrasive) are called pocket stones. Being smaller, they are more portable than bench stones but present difficulty in maintaining a consistent angle and pressure when drawing the stone along larger blades. However, they still can form a good edge. Frequently, fine grained pocket stones are used for honing, especially "in the field". Despite being a homophone with wet, whetstones need be lubricated with neither oil nor water, although it is very common that either is used. Lubrication aids the cutting action and carries swarf away.
Finer grades of whetstones intended for use with oil (though, again, water may also be used) are called oilstones. Oilstones usually come in the form of bench stones. One of the natural minerals commonly used in oilstones is Novaculite. Examples of stones made from this material include Arkansas, Ouachita or Washita stones from the Ouachita Mountains in Arkansas. These come in various grades and colors, with the finer stones being denominated "surgical black" or "pink translucent". Novaculite is from the Devonian and Mississippian periods. It is a low grade metamorphic rock composed mostly of microcrystalline quartz and is basically a recrystallized variety of chert. It is also the primary material in Charnley Forest and Turkey oilstones.
Extremely fine grades of stone that remove very little metal may be called polishing stones.
Read more about this topic: Sharpening Stone