Up to this point minerals had always been classified by their chemical composition. In 1812 Friedrich Mohs created a hardness scale which has subsequently been called the Mohs' scale of mineral hardness.
Mohs Hardness Scale
Among the physical properties of the Diamond that of hardness is pre-eminent ; a quality in which it so exceeds all other bodies that it can penetrate them without being itself even scratched. On the Mohs scale diamond has a hardness of 10 - a diamond is the hardest naturally occurring substance known to man.
Diamonds are Forever...
The Mohs Hardness Table
The Mohs Hardness Scale characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It is easy to understand as Mohs used ordinary materials of known hardness to approximate the position of a mineral on the scale. The Mohs Hardness Scale follows:
Mohs Hardness Scale
Hardness - Name of Mineral - Comparison - Level
1 - Talc - Can be scratched by fingernail - SOFTEST
2 - Gypsum - Can be scratched by fingernail - ↓
3 - Calcite - Can be scratched by a coin - ↓
4 - Fluorite - Can be scratched by a knife blade - ↓
5 - Apatite - Can be scratched by a knife blade - ↓
6 - Orthoclase Feldspar - Harder than Steel - ↓
7 - Quartz - Harder than Steel - ↓
8 - Topaz - Harder than Steel - ↓
9 - Corundum - Harder than Steel - ↓
10 - Diamond - Harder than Steel - HARDEST
Hardness - Bruting
In consequence of its excessive hardness it was formerly only possible to polish it partially, by rubbing it against another rough Diamond a process known as "bruting." In early times there existed so exaggerated an idea of its extraordinary hardness that it was said a Diamond could not be broken by a hammer on an anvil, and that it was far easier to strike the anvil into the earth than to break the Diamond. This will account for the loss of many Diamonds in antiquity, as it was the absurd practice to place them upon the anvil to test their hardness and genuineness. Through this ignorance many a regal gem has been shattered and so lost to the world. It was, of course, only the brittleness of the stone which was really tested by the hammer, and not its hardness, which is a very different quality.
The Hardest Diamonds
The Australian Diamonds are harder and tougher than the stones from India, Borneo and Brazil, while these again have a hardness superior to that of most of the stones from South Africa.
Facts - Information - Guide - Table / Scale - History & Biography of Friedrich Mohs
History & Biography of Friedrich Mohs - Scale - Table - Common Forms
Scale - Bruting - The Hardest Diamonds