Before revision: Artificial sharpening stones are often a bonded abrasive and are readily available as a two sided block, each side being a different grade of grit.
After revision: Silicon Carbide been one of the hardest abrasive with a score of 9.5 on Mohs scale is widely used as abrasive in sand blasting and sand paperArtificial sharpening stones are often a bonded abrasive and are readily available as a two sided block, each side being a different grade of grit.