This chart shows that only Diamonds are harder than Ceramics.
Ceramics are totally non reactive with food! Kyocera advanced ceramic blades offer superior edge retention, holding their edge at least 10 times longer than other professional blades, including high carbon steel. Not all ceramic knives are created equal. Kyoceras micro grain ceramic is more dense, and its cutting edge is sharper, just two reasons that Kyocera is the undisputed worldwide leader in ceramic cutlery. In addition to wear resistance, Kyocera advanced ceramic knives are chemically inert so foods look and taste the way they should. The smooth, polished surface resists germs and is impervious to acids, oils and salts. Clean up is easy, too - simply wash and let dry. Because they are ceramic, Kyocera knives and kitchen tools wont brown foods, they will not transfer a metallic taste or smell, and will never rust. Half the weight of traditional knives and kitchen tools, these products are a joy to use. Suddenly, preparing salads, soups, omelettes and other dishes is fun again. Perfectly balanced and lightweight, Kyocera ceramic knives reduce fatigue during repetitive cutting tasks. Like diamonds and sapphires, the elements of ceramic are formed in nature through thousands of years of crystallization, extreme temperatures, and literally tons of pressure. The result is a pure, dense, unrelenting material that is 50 percent harder than steel, close to diamond in hardness. Each knife purchased from Chef Depot comes with a Lifetime Warranty and free lifetime sharpening! They stay sharp for many years.