1. Minerals

11. Diamond (C) 10 Corundum (Al 2 O 3 ) 9 Topaz (Al 2 SiO 4 (OH-,F-) 2 ) 8 Quartz (SiO 2 ) 7 Orthoclase Feldspar (KAlSi 3 O 8 ) 6 Apatite (Ca 5 (PO 4 ) 3 (OH-,Cl-,F-)) 5 Fluorite (CaF 2 ) 4 Calcite (CaCO 3 ) 3 Gypsum (CaSO 4 ·2H 2 O) 2 Talc (Mg 3 Si 4 O 10 (OH) 2 ) 1 Mineral Hardness

12. Used in jewelry and cutting tools. Four times as hard as corundum. Diamond 10 Sapphire and ruby are varieties of corundum. Twice as hard as topaz. Corundum 9 The November birthstone. Emerald and aquamarine are varieties of beryl with a hardness of 8. Topaz 8 Quartz 7 Orthoclase is a feldspar, and in German, "feld" means "field". Orthoclase 6 When you are hungry you have a big "appetite". Apatite 5 Fluorine in fluorite prevents tooth decay. Fluorite 4 Limestone and most shells contain calcite. Calcite 3 Plaster of paris. Gypsum is formed when seawater evaporates from the Earth’s surface. Gypsum 2 Talcum powder. Talc 1 Associations and Uses Mineral Hardness

13. Hardness of some other items: Hardened steel file 7+ Iron pyrite 6.5 Glass 6-7 Knife blade 5.5 Iron 4-5 Platinum 4-4.5 Copper penny 3 Gold, Silver 2.5–3 Fingernail 2.5