An important figure in the worlds of geology and mineralogy, Friedrich Mohs was born on January 29, 1773 in the town of Gernrode in the Harz Mountains in Germany. The son of a merchant, Mohs was schooled at Halle, and later, at the mining academy at Freiberg. At Freiberg, Friedrich studied under Abraham Werner. Werner instigated a passion inside Mohs, and fueled his love for mineralogy and geognosy.
In the very early 1800's, Mohs picked up two different jobs, both in Austria. He became the foreman at the Neudorf mine in the Harz mountains, as well as a job from banker J.F. van der Nüll. Mohs was to categorize the banker's mineral collection and identify those which had not been identified already. Building on some ideas from botany, Mohs thought that several minerals with similar physical properties came from the same genus, like animals and plants do. However, Mohs was highly rediculed and criticized for this idea, which is not considered to be correct. Mohs was onto something, although it would not come to fruition a few years later.
By 1810, Mohs was becoming tired with his work as a foreman and in 1812, joined the Joanneum at Gratz as a professor of mineralogy. While he would only stay in Gratz for five years, it was more than enough time to finalize what would be his greatest addition to geology, his hardness scale. Mohs realized that certain minerals scratched some minerals and did not scratch others. He noted that a diamond could not be scratched by any other stone, but that other minerals were soft enough to be marked by his fingernail. Mohs Hardness scale is a list of ten minerals, which were picked because they not only represented the hardness well, but because they were so common many collectors would have the minerals in their collection.
- Talc
- Gypsum
- Calcite
- Fluorite
- Apatite
- Feldspar
- Quartz
- Topaz
- Corundum
- Diamond
While an excellent guide, the scale just shows the relative position of the minerals. Diamond is the hardest mineral, but it is 4 times as hard as Corundum (more often known as Ruby or Sapphire) and 6 times as hard as topaz. Mohs' scale is still in place today, and is still frequently used in modernity. However, his scale does not take into account every mineral. Some minerals will have hardness numbers inbetween other numbers, such as uvarovite have a hardness of 7.5. This means that uvarovite can scratch quartz, but not topaz. Other minerals, such as dumortierite, have a hardness range. Dumortierite can have a hardness of 7 or a hardness of up to 8.5. This depends on several different factors such as any other minerals/elements in the stone and how tightly the crystals are packed in the stone.
In 1817, Mohs left Gratz when he heard of Werner's death. Friedrich replaced Werner's position at the mining academy back in Freiberg. He would work here for nine more years before being appointed as a professor of Mineralogy at the University of Vienna and as the superintendent of the Imperial Mineralogical Cabinet. Mohs held on to this position for another nine years, before leaving the cabinet. He was quickly signed on as a mining counsellor at the Mining University in Leoben. Friedrich Mohs died on September 29, 1839 at the age of 63. Mohs was on holiday in Italy at the time.
Sources:
http://www.nhm-wien.ac.at/NHM/Mineral/Mohse.htm
http://www.cartage.org.lb/en/themes/Biographies/MainBiographies/M/Mohs/1.html
http://53.1911encyclopedia.org/M/MO/MOHS_FRIEDRICH.htm
http://geology.about.com/library/bl/blmohsscale.htm
http://www.sciam.com/article.cfm?articleID=000E078D-97A2-1C72-9EB7809EC588F2D7