Friedrich Mohs

Friedrich Mohs
Friedrich Mohs, 1832
Born	29 January 1773 Gernrode, Holy Roman Empire
Died	29 September 1839 (aged 66) Agordo, Kingdom of Lombardy–Venetia
Fields	geology, mineralogy
Known for	Mohs scale of mineral hardness

Carl Friedrich Christian Mohs (German: [moːs]; 29 January 1773 – 29 September 1839) was a German geologist and mineralogist.

Mohs, born in Gernrode, Germany, studied chemistry, mathematics and physics at the University of Halle and also studied at the Mining Academy in Freiberg, Saxony. After assuming the position of a foreman at a mine in 1801, Mohs moved in 1802 to Austria, where he was employed in trying to identify the minerals in a private collection of a banker. In 1812 he moved to Graz where he was employed by Archduke Johann in his newly established museum and science academy, which was subsequently divided into the Joanneum and the Graz University of Technology

As part of this task, he started classifying minerals by their physical characteristics, in spite of their chemical composition, as had been done traditionally. This emphasis on physical characteristics was at odds with the prevailing chemical systematics. However, both Theophrastus and Pliny the Elder had compared the relative hardness of minerals known to them in the ancient world, including diamond and quartz. They knew that diamond could scratch quartz, so showing it to be harder. This became the basis of the hardness scale developed by Mohs. The hardest mineral, diamond was given a value of 10 and softer minerals such as talc were given the very low value of 1 (unity). Other minerals were given intermediate values, depending on their ability to scratch another mineral in the scale. Thus gypsum was given the value 2 because it will scratch talc crystals, and calcite the value 3 because it will scratch gypsum. Minerals are also now classified by chemical characteristics, but the physical properties are still useful in field examination.