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What is the Mohs
Hardness Scale
What is the Mohs Hardness Scale? The Mohs Hardness Scale characterizes
the scratch resistance of various minerals through the ability of a
harder material to scratch a softer material.
Mohs Hardness
Scale - History & Biography of Friedrich Mohs (1773 - 1839)
The Mohs Hardness Scale is named after Friedrich Mohs (1773 - 1839) who
was a German geologist. Friedrich Mohs studied physics, chemistry and
mathematics at University and then continued his studies at the Mining
Academy in Freiberg. His interest in diamonds started in earnest in 1801
when he became a foreman at a mine. Friedrich Mohs then moved to Austria
identifying the minerals in a private collection of a Banker. During
this time he developed a system for classifying minerals by their
physical characteristics. 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.
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 |
|
Table / Scale |
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.
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
Mohs Hardness Scale
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