What are sharpening stones made of?

9th March 2020

What are sharpening stones made of?
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			Sharpening stones are typically made from one of three materials – novaculite, aluminium oxide, or silicon carbide. Traditional oil stones are natural stones commonly made from novaculite. These types of stone were chiefly quarried in Arkansas, which is where the “Arkansas Stone” derives its name. Natural stones are rarely quarried now as synthetic stones are easier and cheaper to make.

			Novaculite Novaculite is a type of sedimentary rock. It is made up of microcrystalline quartz and varies from white-grey to grey-black in colour. Its micro-crystal structure makes it very hard and dense, which is why it is perfect for use as a sharpening stone.

			Aluminium Oxide Aluminium oxide is a chemical compound made up of aluminium and oxygen. It is frequently found in its crystalline form, varieties of which make up precious stones such as sapphire and ruby, though is mass produced as a powder for use as an abrasive.

			Silicon Carbide Silicone carbide is a chemical compound combining silicon and carbon. It also known as carborundum. Although rarely forming in nature, it is manufactured as a powder for use as an abrasive. Powdered abrasives are formed into solid blocks or “stones” by a process called sintering.

			Sintering
			Sintering is a process whereby powder particles are formed into a solid mass by compression and heat.

			A sharpening stone is made of thousands of tiny particles that have been compressed together using the process of sintering.

			As a tool or blade is drawn across the stone, these particles abrade the metal to varying degrees, depending on the size of the grit particles.