This is a picture of several tools, both modern and ancient, manufactured from the famous Arkansas Novaculite. Novaculite is an extremely hard sedimentary rock made almost purely of silica (99.9%). It is similar to chert except that it is harder and even more silica-rich; it is possible that novaculite is formed from the metamorphosis of chert, though its genesis is uncertain.
Novaculite (from Latin, meaning razor stone) has been prized since prehistoric times as a material for making stone tools like knives and arrowheads. Since at least the early 1800s novaculite has been utilized as an abrasive material for sharpening knives and other tools.
The manufacture of whetstones, or sharpening stones, from novaculite continues to be a thriving business in the Hot Springs, Arkansas area today.