What material is commonly used to sharpen knives?

Carborundum stones, also known as silicon carbide stones, are commonly used to sharpen knives due to their hardness and effectiveness in grinding and honing the steel of the blade. They are designed to create a fine edge by removing material from the knife, which is essential for maintaining sharpness. The gritty surface of carborundum stones allows for efficient sharpening, making them a favorite among both professional chefs and home cooks.

Other materials, such as diamond stones, are also effective for sharpening but are usually considered a different type of sharpening stone due to their unique properties. Pumice stones are typically softer and are more suitable for other applications, such as skincare, rather than for sharpening tools. Sandpaper could be used in a pinch but is generally not recommended for knife sharpening due to its inconsistency and potential to produce uneven edges.