Friedrich MohsDied 29 Sep 1839 at age 66 (born 29 Jan 1773).German mineralogist who devised the Mohs scale to compare mineral harness, illustrated by ten common or readily-available minerals. They are ranked by which can scratch another. At the beginning of his scale, 1 to 3, are talc, gypsum and calcite. At the top, the hardest 8 to 10, are topaz (including emerald and aquamarine), corundum (including as varieties sapphire and ruby) and diamond. Diamond is known for its common use to edge cutting tools, because it is four times as hard than even corundum. Interestingly, gold and silver come in the 2.5 to 3 range, which is comparable to the hardness of a fingernail (2.5). Mohs proposed this non-linear hardness scale in 1812, after spending a year as curator organizing an institution's mineral collection. By 1820, his scale was widely used by mineralogists, and he contined to refine it.« |
