The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science.The method of comparing hardness by seeing which minerals can scratch others, however, is of great antiquity, having first been mentioned circa 300 BC,

 

For more information about Mohs scale try these links:

http://www.amfed.org/t_mohs.htm

http://chemistry.about.com/od/geochemistry/a/mohsscale.htm

http://www.minsocam.org/msa/collectors_corner/article/mohs.htm