Silicon carbide sandpaper

Silicon carbide is sharper and harder than standard forms of aluminum oxide. It has needle-like grains that resemble shards of broken glass. These hard, sharp grains cut glass, plastic, and metal well under light pressure, but silicon carbide is not a tough mineral. Silicon carbide sandpaper removes material more quickly than aluminum oxide but doesn't last as long. Use it on metal, coated wood, plastic and for tasks, such as rough sanding, paint or rust removal and sanding between coats when finishing. Its elongated shape shears off easily, making it too friable for bare-wood sanding because the abrasive wears down too quickly, according to manufacturers. It is, however, an excellent choice for smoothing a finish between coats and for rubbing out film finishes like lacquer and shellac, because it cuts quickly and produces a uniform scratch pattern. Also, waterproof versions won’t degrade when used with water or oil. For these reasons, it’s also most commonly found in fine grit rather than coarse.

Source: https://www.finehomebuilding.com/2011/11/10/whats-the-difference-aluminum-oxide-silicon-carbide-and-ceramic