Mohs Scale of Mineral Hardness

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MOH’s SCALE OF HARDNESS
4(A-D)
Invented in 1812 Developed by German Mineralogist Frederich Moh’s5

MINERAL6

HARDNESS

NOTES

 

 

 

Talc

1 (1.5) 1

Fingernail is stronger and will scratch it

Gypsum

2 (2.5) 1

Fingernail is stronger and will scratch it

Calcite

3 (3.5) 1

Copper penny is harder and will scratch it

Fluorite

4 (4.5) 1

Steel will scratch it

Apatite

5 (5.5) 1

Steel will scratch it

Orthoclase (Feldspar)

6 (6.5) 1

Steel will not scratch it easy.  Feldspar will scratch Silica (Glass) 2

Quartz

7 (7.5) 1

Hardest most abundant and common mineral that will scratch steel / Silica (Glass)

Topaz

8 (8.5) 1

Considered be harder than any common mineral known

Corundum

9 (9.5) 3

Will scratch other known minerals above this hardness level

Diamond

10 (10.5) 1, 2

Will scratch any known mineral including diamond itself.

 

  1. Although the Moh’s Scale of Hardness is primarily made up of Hardness Numbers from 1-10, it should be noted that we have for the sake of our table referenced a .5 to each one. As it is that the Mineral will scratch itself, for example, a Diamond will scratch a Diamond it can be stated that the Hardness of a Diamond is Really 10.5 instead of 10. The same goes for the other minerals in the group.

  2. Silica which Glass (quartz is part of the combination) is made up of is rated at this level at the hardness factor of around 6. Normal window pane glass comes in at about 5.5 on the scale. It should be noted that Quartz in this sense does however scratch glass. In relation, quartz will cut glass but like easing a hot knife through butter, a diamond will also cut it but much more easily and more precisely. You might say that Quartz in this sense will scratch glass but a Diamond will easily “cut” it.

  3. There is a common misnomer that to see if you have a true and real Diamond in times past, you could test it by scratching Silica (Quartz). As we can see from this Table, Glass itself in the Quartz family for the most part, will actually scratch itself (refer to note 1). Equally, our table shows that all minerals rated 6 and above are also capable of scratching glass as well.


  1. One may think that the hardness of a mineral is the same between 1 and 2 as it would be between for example, 9-10; however, this is not so. For example, on the scale of Hardness for a Diamond, a Diamond is around 15 x harder than a Sapphire (corundum).

 

  1. Also in scale of hardness it is noted that each mineral in the scale will scratch all other minerals below it; including itself. It should be noted that this scale is for general reference purposes only and is used by many today and even has some use for materials engineers and metallurgists, but overall is not very helpful to them. It should be noted also that larger specimens of mineral may be softer than single smaller crystals of the same mineral. It should be noted that most gemstones are rated at 7 and above.

 

  1. When testing for the hardness of a mineral as to whether it will indeed scratch another don’t be surprised or extend belief in dust on the mineral after you attempt to scratch it. Don’t believe in other words that it did actually scratch it; it may be that the mineral actually scratched the other that attempted to scratch it.

 

  1. Blow on it, or rub it, to make sure it is not just dust and is truly a scratch. Equally to ensure, if you are not sure, clean the stone and dry it and then look at it again; preferably with at least a magnifying glass (we would prefer a 10x loupe that will show much greater detail).

 

  1. It should be noted that there are reports that some believe that that the Mohs Hardness Scale was invented in 1812 by German Mineralogist Frederich Moh’s – A scale that has been debated as being arbitrary as it is not truly a linear one. Other sources contend that Frederich Moh’s invented the scale in 1822.

    As to which account is the most logical, there seems to be a debate as to when it was actually invented. Perhaps as we like to believe, the scale was invented in 1812 but did not gain any popularity or generalized usage until around 1822. Historically there are many accounts for this relationship so your guess is as good as ours.


It is much like Homer’s Lliad and Odyssey, some relate that it could not have come to be in its true form as Caesar did not allow for writing except for official documents, at least on manuscript of papyrus. Then again, others relate that this they are in their “entirety” true works by Homer. Again, your guess would be as good as ours.

Names used for the scale have been Moh’s Scale of Mineral Hardness, Mohs Scale, Moh’s Hardness Scale, Mohs Scale of Mineral Hardness, Mohs, moh’s and hardness; one thing we can ascertain with facts is that it is certainly something that is hotly debated and may in light of the great Mineralogist, remain very much a true mystery as things of nature should. Only when man intervenes does it become hotly debated and the real nature overshadowed.

  1. Relative Hardness of the Minerals Contained in the Table And Their Chemical Properties

    1 Talc (Mg3Si4O10(OH)2)
    2 Gypsum (CaSO4·2H2O)
    3 Calcite (CaCO3)
    4 Fluorite (CaF2)
    5 Apatite (Ca5(PO4)3(OH-,Cl-,F-))
    6 Orthoclase (Feldspar) (KAlSi3O8) (Many refer to this as Feldspar or just Orthoclase)
    7 Quartz (SiO2) (Really just a form of Silicon Dioxide and is used in the making of glass)
    8 Topaz (Al2SiO4(OH-,F-)2)
    9 Corundum (Al2O3) (Ruby and Sapphire7)
    10 Diamond (C)

 

  1. Most relate that when it comes to Corundum gems, if it is not red, it has got to be a Sapphire. We are not totally in agreement with this but it is the general standard that is used.

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