Mohs scale of mineral hardness
A ceramic knife is a knife designed with a ceramic blade typically made from zirconium dioxide (ZrO2; also known as zirconia). These knife blades are usually produced through the dry-pressing and firing of powdered zirconia using solid-state sintering. It is 8.5 on the Mohs scale of mineral hardness, compared to 4.5 for normal steel and 7.5 to 8 for hardened steel and 10 for diamond. The resultant blade has a hard edge that stays sharper for longer when compared to conventional steel knives. While the edge is harder than a steel knife, it is more brittle. The ceramic blade is sharpened by grinding the edges with a diamond-dust-coated grinding wheel.