Our stones are composite materials made of ceramic and corundum and offer a very long service life without noticeable wear. The hardness of our stones is 9.0 MOH compared to 6.0 MOH for granite or a diamond with 10.0 MOH. An important result of the dissertation (doctoral thesis) published in 1995 on "stone disk mills" is: the harder the stone, the gentler the milling process of the grains. Because for gentle milling, the difference between the hardness of the milling stones and the hardness of the grist is crucial. The greater this difference, the gentler and better the milling process.
Corundum is used in many medical implants, dental and surgical tools, and other common applications (including dietary supplements). There is no risk of toxicity.