Mohs scale of mineral hardness
Introduction
The Mohs scale of mineral hardness is a qualitative ordinal scale that characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer one. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science.
History
Mohs, born in 1773, was a German geologist and mineralogist. He studied at the Mining Academy of Freiberg, Saxony. His contribution to the field of mineralogy was significant, with the Mohs scale of mineral hardness being his most notable achievement.
Principles
The Mohs scale of hardness is based on the ability of one natural sample of matter to scratch another. The samples of matter used by Mohs are all different minerals. Minerals are chemically pure solids found in nature. Rocks are made up of one or more minerals.
The Mohs scale is a purely ordinal scale. For example, corundum (9) is twice as hard as topaz (8), but diamond (10) is four times as hard as corundum. The scale is logarithmic.
Scale of mineral hardness
The Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly. The samples of matter used by Mohs are all different minerals. Minerals are pure substances found in nature. The table below shows Mohs' scale of hardness with examples of each mineral:
- Talc
- Gypsum
- Calcite
- Fluorite
- Apatite
- Orthoclase feldspar
- Quartz
- Topaz
- Corundum
- Diamond
Use and importance
The Mohs scale of hardness is used by geologists and gemologists as a simple way of identifying minerals. It is also used in materials science to compare the hardness of different materials.
Limitations
While greatly facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting.