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The Mohs scale is an ordinal scale. For example, corundum (9) is twice as hard as topaz (8), but diamond (10) is four times as hard as corundum. [ citation needed ] The table below shows the comparison with the absolute hardness measured by a sclerometer , with images of the reference minerals in the rightmost column.
The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 1 as the hardness of talc, the softest mineral. When scraped on a streak plate , talc produces a white streak, though this indicator is of little importance, because most silicate minerals produce a white streak.
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Mohs's scale had two limitations: it was not linear, and most modern abrasives fall between 9 and 10.; [6] [7] so, later scientists attempted to increase resolution at the harder end of the scale. Raymond R. Ridgway, a research engineer at the Norton Company, modified the Mohs scale by giving garnet a hardness of 10 and diamond a hardness of 15.
Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third-hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers ...
Three polytypes of chrysotile are known. [8] These are very difficult to distinguish in hand specimens, and polarized light microscopy [6] must normally be used. Some older publications refer to chrysotile as a group of minerals—the three polytypes listed below, and sometimes pecoraite as well—but the 2006 recommendations of the International Mineralogical Association prefer to treat it as ...
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms.It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology ...