Mohs scale

noun

1. an arbitrary scale used to indicate relative hardness, arranged in 10 ascending degrees: 1, talc; 2, gypsum; 3, calcite; 4, fluorite; 5, apatite; 6, orthoclase; 7, quartz; 8, topaz; 9, corundum; 10, diamond
2. a modification of this scale, retaining its first six minerals and continuing: 7, pure silica glass; 8, quartz; 9, topaz; 10, garnet; 11, fused zircon; 12, corundum; 13, silicon carbide; 14, boron carbide; 15, diamond

Etymology: after F. Mohs (1773-1839), Ger mineralogist