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Mohs based the scale on ten readily available minerals. Materials are characterised against the scale by finding the hardest material that they can scratch.
The table below shows comparison with absolute hardness measures by a sclerometer. Mohs' is a purely ordinal scale with, for example, corundum being twice as hard as topaz, but diamond, almost four times as hard as corundum.
| Hardness | Mineral | Absolute Hardness |
|---|---|---|
| 1 | Talc (Mg3Si4O10(OH)2) | 1 |
| 2 | Gypsum (CaSO4·2H2O) | 3 |
| 3 | Calcite (CaCO3) | 9 |
| 4 | Fluorite (CaF2) | 21 |
| 5 | Apatite (Ca5(PO4)3(OH-,Cl-,F-)) | 48 |
| 6 | Orthoclase Feldspar (KAlSi3O8) | 72 |
| 7 | Quartz (SiO2) | 100 |
| 8 | Topaz (Al2SiO4(OH-,F-)2) | 200 |
| 9 | Corundum (Al2O3) | 400 |
| 10 | Diamond (C) | 1500 |
The mnemonicA mnemonic ( SAMPA /n@'mAnIk/ in US or /n@'mQnIk/ in UK) is a memory aid. Mnemonics are often verbal, are sometimes in verse form, and are often used to remember lists. Mnemonics rely not only on repetition to remember facts, but also on creating associat traditionally taught to geology students to remember this table is "The Girls Can Flirt And Other Queer Things Can Do."
An alternative table is shown below which has been modified to incorporate additional substances that may fall in between two levels.
| Hardness | Mineral |
|---|---|
| 1 | LiquidOne of the four phases of matter, a liquid is a fluid whose volume is fixed under conditions of constant temperature and pressure; and, whose shape is usually determined by the container it fills. Furthermore, liquids exert pressure on the sides of a cont |
| 2 | Gypsum |
| 3 | Calcite |
| 4 | Fluorite |
| 5 | Apatite |
| 6 | Orthoclase |
| 7 | Vitreous pure silica |
| 8 | Quartz |
| 9 | Topaz |
| 10 | GarnetThe Garnet group of minerals show crystals with a habit of dodecahedrons and trapezohedrons. They are nesosilicates with the same general formula, AB(SiO). Many different chemical elements are included in the several varieties of garnet, including calcium |
| 11 | Fused zirconiaZirconia ( Zr O) is a white crystalline oxide of zirconium that is used as a refractory, in insulation, abrasives, enamels and glazes. Zirconia is one of the most studied ceramic materials. Pure ZrO has a monoclinic crystal structure at room temperature a |
| 12 | Fused alumina |
| 13 | Silicon carbide |
| 14 | Boron carbide |
| 15 | Diamond |