Water stones are a tried-and-true tool used to repair, sharpen, and polish kitchen knives.
Synthetic or artificial whetstones are made with bonded abrasives. These are commonly aluminium oxide, silicon carbide (a type of ceramic), or a diamond coating mounted on a metal sheet. Synthetic whetstones offer a consistent grit size, which allows for faster, more effective sharpening.
Natural whetstones are typically formed of quartz, such as novaculite. The Ouachita Mountains in Arkansas are noted as a source for these. Novaculite is also found in Syria and Lebanon, previously a part of the Ottoman (Turkish) empire.
Often whetstones are used with a cutting fluid to enhance sharpening and carry away swarf. Those used with water for this purpose are often called water stones or waterstones.