Among the natural gems only moissanite and diamond are harder, with diamond having a Mohs hardness of 10.0 and moissanite falling somewhere in between corundum (ruby) and diamond in hardness. Source: Internet
Because of weak bonding between the layers, gray arsenic is brittle and has a relatively low Mohs hardness of 3.5. Source: Internet
Characteristics Physical properties In its pure form, molybdenum is a silvery-grey metal with a Mohs hardness of 5.5. Source: Internet
Dyar and Gunter, pp. 32–39 Chesterman and Lowe, p. 38 Hardness main Diamond is the hardest natural material, and has a Mohs hardness of 10. The hardness of a mineral defines how much it can resist scratching. Source: Internet
Chalcopyrite is brighter yellow with a greenish hue when wet and is softer (3.5–4 on Mohs' scale). Source: Internet
Common, non-architectural grades of soapstone can just barely be scratched with a fingernail and are thus considered to have a hardness of 2.5 on the Mohs scale. Source: Internet