Is 10th harder than 12th.

Mohs hardness - The hardness of minerals

There are very soft minerals like talc that can be scratched with a fingernail. But there are also minerals of medium hardness and there are very hard minerals such as diamonds, the hardest of all known minerals. The reason for the different hardnesses: the structure of the crystal lattice.

Table of contents Mohs hardness

A geologist and the hardness of minerals

The term used in mineralogy Mohs hardness (English: hardness, Mohs scale) was named after the geologist Friedrich Mohs (1773 to 1839). On the basis of the Mohs' hardness scale, all minerals are divided into ten different degrees of hardness, which correspond to the Resistance of the mineral when scratching with sharp-edged objects specify.

The 10 degrees of hardness of minerals

According to the Mohs hardness scale, the mineral with the lowest hardness is talc with a Mohs hardness of 1. With a hardness of 10, diamonds are the hardest minerals on earth.

Minerals with a hardness from 10 to 1 can always scratch the previous, softer mineral - but not the other way around. That means: a diamond can leave scratches on the surface of talc, but talc cannot scratch any marks on diamond crystals.
The reason for the different degrees of hardness of minerals is the inner structure of the minerals, the crystal lattice, which increases with increasing Mohs hardness.

Soft, hard and very hard minerals

Based on the Mohs scale, minerals are the

  • hardness 1 to 2 as soft classified
  • those of hardness 3 to 6 as medium hard
  • Hardening of over 6 as hard
  • over 8 as very hard or as minerals with Gemstone hardness classified

Determination of hardness

So-called hardness determination boxes or a hardness scale, which are equipped with the respective reference minerals corresponding to the hardness, are suitable for verifying the hardness.

The minerals to be tested can be checked for hardness with the comparison pieces.

Objects from everyday life are also suitable as a quick test.

For example, soft minerals (talc - 1, gypsum spar - 2) can be scratched with the fingernail.
Medium-hard minerals (calcite - 3, fluorite - 4, apatite - 5) are harder and harder to scratch with a knife.

Minerals with a hardness of 6 (orthoclase) can be scratched with steel files, the hardness 7 (quartz) scratches window glass.

In the case of hard minerals, comparison minerals can be used for determination. Topaz with a hardness of 8 scratches quartz without any problems, while corundum (hardness 9) scratches topaz.

The diamond with a hardness of 10, on the other hand, cannot be scratched.

Causes of the hardness of minerals

The hardness of minerals can vary within a few minerals. The reason for this are different resistances in different directions. An example of a mineral that has two different degrees of hardness at the same time is thistle. However, other, harder minerals can also have grown as inclusions on and in minerals, which lead to different hardnesses within a mineral. And the aggregates can also influence the Mohs hardness, whereby, for example, massive minerals are harder than minerals with a needle-like, filigree habit.

Degree of hardnessmineral
1Realgar, selenite, talc, auripigment
2Silver, sulfur, antimonite, boulangerite, galena, halite, crocoite, muscovite, creaseyite
3Gold, zinc blende, calcite, rhodochrosite, barium pharmacosiderite, scorodite, wulfenite, pyromorphite, roselite, vauquelinite
4Kinoite, fluorite, aragonite, siderite, azurite, malachite, coronadite, stilbit, okenite, purpurite
5Eudialyte, Brewsterite, Magnetite, Opal, Smithsonite, Turquoise, Lapis Lazuli, Natrolite, Actinolite, Hemimorphite
6Pyrite, marcasite, hematite, agate, rhodonite, sodalite, prehnite, orthoclase
7Cassiterite, rock crystal, cordierite, amethyst, tiger's eye, zircon, olivine, almandine, tourmaline, rose quartz, tanzanite
8Beryl, emerald, topaz, pyknite
9Corundum - ruby ​​and sapphire

Table: List of different minerals and their Mohs hardness

However, one must note that the Mohs hardness only allows relative statements, i.e. shows which mineral is scratched by another. There is also the risk of damaging minerals, since the hardness test should be carried out on fresh crystal surfaces if possible.
An alternative in terms of accuracy is the Knoop scale, which allows statements about hardness by exposing a mineral to the pressure of a defined weight of lead and compressing it.

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See also:
⇒ Fake gems and minerals
⇒ Rare minerals
⇒ Medenbach and Sussieck-Fornelfeld: "Steinbach's natural guide minerals"

⇒ Booth, B. (1999): Stones and Minerals. Koenemann Verlag Cologne
⇒ Pellant, C. (1994): Stones and Minerals. Ravensburger nature guide. Ravensburger Buchverlag Otto Maier GmbH
⇒ Bauer, J .; Tvrz, F. (1993): The Cosmos Mineral Guide. Minerals rocks precious stones. An identification book with 576 color photos. Gondrom Verlag GmbH Bindlach
⇒ Medenbach, O .; Sussieck-Fornefeld, C .; Steinbach, G. (1996): Steinbach's natural guide minerals. 223 species descriptions, 362 color photos, 250 drawings and 30 pages of identification tables. Mosaik Verlag Munich
⇒ Schumann, W. (1992): Precious and precious stones: all precious and precious stones in the world; 1500 unique pieces. BLV determination book, BLV Verlagsgesellschaft mbH Munich
⇒ Schumann, W. (1991): Minerals rocks - characteristics, occurrence and use. FSVO nature guide. BLV Verlagsgesellschaft mbH Munich

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Last updated: October 28, 2020

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