A scale for classifying minerals based on relative hardness, determined by the ability of harder minerals to scratch softer ones. The scale includes the following minerals, in order from softest to hardest: 1. talc; 2. gypsum; 3. calcite; 4. fluorite; 5. apatite; 6. orthoclase; 7. quartz; 8. topaz; 9. corundum; 10. diamond.