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| | Mohs scale of mineral hardness - Wikipedia, the free encyclopedia |
 | | It was created, in 1812, by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science. |
 | | The hardness of a material is measured against the scale by finding the hardest material that that the given material can scratch, and/or the softest material that can scratch the given material. |
 | | Corundum (Al Diamond (C) On the Mohs scale, fingernail has hardness 2; copper penny, about 3; a knife blade, 5; window glass, 5.5; steel file, 6.5. |
| en.wikipedia.org /wiki/Mohs_scale_of_mineral_hardness (278 words) |
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