Doug Menadue :: Bespoke Gems - Precision Hand Faceted Gemstones Of The Highest Quality

Moh's Hardness Scale

Fanta Orange Spessartite Garnet, Acorn, #220 The Moh's hardness scale is a relative hardness scale and is used as a simple indicator of a stone's hardness relative to others. It was developed by the Viennese mineralogist, Friedrich Mohs (1773-1839).

Generally, stones with are hardness of 7 or above are considered suitable for everyday jewellery wear.

Stones 6 or less are considered soft and are prone to easily scratching. This is not to say such stones cannot be used in jewellery but if worn, keep in mind that they must be handled carefully. These stones can be damaged by dust, as dust contains small particles of quartz which has a Moh's hardness of 7.

A better indicator of the actual increase of hardness within the scale is the cutting resistance or Rosiwal number. This in effect is an absolute hardness scale.

Mohs Stone Test Rosiwal
10 Diamond 140,000
9 Corundum, Sapphire, Ruby 1,000
8 Topaz, Spinel, Beryl(-), Aquamarine(-), Emerald(-) 175
7 Quartz, Amethyst, Citrine, Tourmaline(+), Garnet(+-) Scratches window glass 120
6 Orthoclase Can be scratched with steel file 37
5 Apatite Can be scratched with knife 6.5
4 Fluorite Easily scratched with knife 5
3 Calcite Can be scratched with copper coin 4.5
2 Gypsum Can be scratched with fingernail 1.25
1 Talc Can be scratched with fingernail 0.03

* Where a stone has (+) hardness can vary up to 0.5, eg. Tourmaline has Moh's hardness of 7-7.5
* Where a stone has (-) hardness can vary up to -0.5, eg. Emerald has Moh's hardness of 7.5-8

 

 

 

 

 

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