Mohs hardness
Information about Mohs hardness
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science.
Mohs based the scale on ten minerals that are all readily available. As the hardest known naturally occurring substance, diamond is at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, and/or the softest material that can scratch the given material. For example, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fall between 4 and 5.
The Mohs scale is a purely ordinal scale. For example, corundum (9) is twice as hard as topaz (8), but diamond (10) almost four times as hard as corundum. The table below shows comparison with absolute hardness measured by a sclerometer.
On the Mohs scale, a pencil lead has a hardness of 1; a fingernail has hardness 2.5; a copper penny, about 3.5; a knife blade, 5.5; window glass, 5.5; steel file, 6.5.[1] Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale.
The table below incorporates additional substances that may fall between levels:
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, and chlorapatite, named for high concentrations of OH-, F-, or Cl-
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Mohs based the scale on ten minerals that are all readily available. As the hardest known naturally occurring substance, diamond is at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, and/or the softest material that can scratch the given material. For example, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fall between 4 and 5.
The Mohs scale is a purely ordinal scale. For example, corundum (9) is twice as hard as topaz (8), but diamond (10) almost four times as hard as corundum. The table below shows comparison with absolute hardness measured by a sclerometer.
| Hardness | Mineral | Absolute Hardness |
|---|---|---|
| 1 | Talc (Mg3Si4O10(OH)2) | 1 |
| 2 | Gypsum (CaSO4·2H2O) | 2 |
| 3 | Calcite (CaCO3) | 9 |
| 4 | Fluorite (CaF2) | 21 |
| 5 | Apatite (Ca5(PO4)3(OH-,Cl-,F-)) | 48 |
| 6 | Orthoclase Feldspar (KAlSi3O8) | 72 |
| 7 | Quartz (SiO2) | 100 |
| 8 | Topaz (Al2SiO4(OH-,F-)2) | 200 |
| 9 | Corundum (Al2O3) | 400 |
| 10 | Diamond (C) | 1500 |
On the Mohs scale, a pencil lead has a hardness of 1; a fingernail has hardness 2.5; a copper penny, about 3.5; a knife blade, 5.5; window glass, 5.5; steel file, 6.5.[1] Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale.
The table below incorporates additional substances that may fall between levels:
| Hardness | Substance or Mineral |
|---|---|
| 1 | Talc |
| 2 | Gypsum |
| 2.5 to 3 | pure Gold, Silver, Aluminum |
| 3 | Calcite, Copper penny |
| 4 | Fluorite |
| 4 to 4.5 | Platinum |
| 4 to 5 | Iron |
| 5 | Apatite |
| 6 | Orthoclase |
| 6 | Titanium |
| 6.5 | Iron pyrite |
| 6 to 7 | Glass, Vitreous pure silica |
| 7 | Quartz |
| 7 to 7.5 | Garnet |
| 7 to 8 | Hardened steel |
| 8 | Topaz |
| 9 | Corundum |
| 10 | Diamond |
| >10 | Ultrahard Fullerite |
| >10 | Aggregated diamond nanorods |
Notes
1. ^ "The Hardness of Minerals and Rocks" by William S. Cordua. Lapidary Digest (1998). Retrieved on 2007-08-19. Hosted at International Lapidary Association
References
- American Federation of Mineralogical Societies. "Mohs Scale of Mineral Hardness". Last Revised on April 21, 2007. Retrieved on August 19, 2007.
- Cordua, William S. "The Hardness of Minerals and Rocks". Lapidary Digest, c. 1998.
A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties.
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19th century - 20th century
1780s 1790s 1800s - 1810s - 1820s 1830s 1840s
1809 1810 1811 - 1812 - 1813 1814 1815
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Subjects: Archaeology - Architecture -
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1780s 1790s 1800s - 1810s - 1820s 1830s 1840s
1809 1810 1811 - 1812 - 1813 1814 1815
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Subjects: Archaeology - Architecture -
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Mineralogy is an Earth Science focused around the chemistry, crystal structure, and physical (including optical) properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical
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Friedrich Mohs (January 29, 1773 - September 29, 1839) was a German geologist/mineralogist. Mohs, born in Gernrode, Germany, studied chemistry, mathematics and physics at the University of Halle and also studied at the Mining Academy in Freiberg, Saxony.
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Hardness refers to various properties of matter in the solid phase that give it high resistance to various kinds of shape change when force is applied. Hard matter is contrasted with soft matter.
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Materials science or materials engineering is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering. This science investigates the relationship between the structure of materials and their properties.
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ordinal, ordinal number, and transfinite ordinal number refer to a type of number introduced by Georg Cantor in 1897, to accommodate infinite sequences and to classify sets with certain kinds of order structures on them.
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Corundum (from Tamil kurundam) is a crystalline form of aluminium oxide and one of the rock-forming minerals. It is naturally clear, but can have different colors when impurities are present.
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Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. It crystallizes in the orthorhombic group and its crystals are mostly prismatic terminated by pyramidal and other faces, the basal pinacoid often being
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The sclerometer (from the Ancient Greek σκλερος meaning "hard") is an instrument used by mineralogists to measure the scratch hardness of materials. It was invented by Turner in 1896.
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Talc (derived from the Persian via Arabic talq) is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2.
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Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O.
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Crystal varieties
Gypsum occurs in nature as flattened and often twinned crystals and transparent cleavable masses called selenite...... Click the link for more information.
calcite]] The carbonate mineral, calcite, is a chemical or biochemical calcium carbonate corresponding to the formula CaCO3 and is one of the most widely distributed minerals on the Earth's surface.
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Fluorite (also called fluorspar) is a mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon.
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- ''Not to be confused with appetite, the desire to eat.
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, and chlorapatite, named for high concentrations of OH-, F-, or Cl-
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Orthoclase (endmember formula KAlSi3O8) is an important tectosilicate mineral, which forms igneous rock. It is also known as alkali feldspar and is common in granite and related rocks.
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Quartz (from German Quarz [1]) is the second most common mineral in the Earth's continental crust, feldspar being the first.
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Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. It crystallizes in the orthorhombic group and its crystals are mostly prismatic terminated by pyramidal and other faces, the basal pinacoid often being
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Corundum (from Tamil kurundam) is a crystalline form of aluminium oxide and one of the rock-forming minerals. It is naturally clear, but can have different colors when impurities are present.
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Diamond is an allotrope of carbon. It is the hardest known natural material and the third-hardest known material after aggregated diamond nanorods and ultrahard fullerite. Its hardness and high dispersion of light make it useful for industrial applications and jewelry.
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nail is a horn-like structure at the end of a human's or an animal's finger or toe. See also claw.
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Parts of the nail
Anatomically fingernails and toenails..... Click the link for more information.
A file (or hand-file) is a hand tool used to shape material by cutting. A file typically takes the form of a hardened steel bar, mostly covered with a series of sharp, parallel ridges or teeth.
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Talc (derived from the Persian via Arabic talq) is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2.
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Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O.
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Crystal varieties
Gypsum occurs in nature as flattened and often twinned crystals and transparent cleavable masses called selenite...... Click the link for more information.
GOLD refers to one of the following:
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- GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade).
- GOLD (parser) is an open source BNF parser.
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Silver (IPA: /ˈsɪlvə(ɹ)/) is a chemical element with the symbol Ag (Latin: argentum) and atomic number 47.
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Aluminium (IPA: /ˌæljʊˈmɪniəm/, /ˌæljəˈmɪniəm/) or aluminum (IPA: /əˈluːmɪnəm/
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calcite]] The carbonate mineral, calcite, is a chemical or biochemical calcium carbonate corresponding to the formula CaCO3 and is one of the most widely distributed minerals on the Earth's surface.
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2, 1
(mildly basic oxide)
Electronegativity 1.90 (Pauling scale)
Ionization energies
(more) 1st: 745.5 kJmol−1
2nd: 1957.9 kJmol−1
3rd: 3666 kJmol−1
Atomic radius 135 pm
Atomic radius (calc.
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(mildly basic oxide)
Electronegativity 1.90 (Pauling scale)
Ionization energies
(more) 1st: 745.5 kJmol−1
2nd: 1957.9 kJmol−1
3rd: 3666 kJmol−1
Atomic radius 135 pm
Atomic radius (calc.
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penny (pl. pence or pennies) is a coin or a unit of currency used in several English-speaking countries.
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Value
The penny is among the lowest denomination of coins in circulation...... Click the link for more information.
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