What is the Mohs Hardness Scale and why is it important for your jewellery?
The Mohs Scale of Hardness was a system devised by German chemist Fredrich Mohs, in 1812, to test the relative hardness of minerals. The Scale consists of a list of ten minerals which are arranged in order of hardness compared to each other and runs from Talc being very soft at number 1, to Diamond which is the hardest mineral at number 10.
The ten minerals, in order, on Mohs Hardness Scale are:
- 1. Talc
- 2. Gypsum
- 3. Calcite
- 4. Flourite
- 5. Apatite
- 6. Orthoclase
- 7. Quartz
- 8. Topaz
- 9. Corundum
- 10. Diamond
How the Mohs Scale is Used
To use the scale a mineral is compared to the minerals on the scale by scratching it with the mineral. If the mineral being tested is harder than the mineral it is being compared to, it will leave a scratch on the surface of the other mineral.
The relative hardness of a mineral is determined by the highest number mineral on the scale that it can scratch. For example, if a mineral can scratch a piece of quartz (which has a hardness of 7 on the scale) but not a piece of topaz (which has a hardness of 8 on the scale), its hardness would be assigned a value of 7 on the scale.
The Mohs hardness scale is widely used in mineralogy and materials science as a simple and convenient way to determine the relative hardness of a mineral. The Scale is in widespread use all over the world, even today – you will notice that in every article we write on gemstones we will tell you its hardness according to the Mohs Hardness Scale.
The scale has helped jewellery makers and designers in the past to know what minerals were suitable for different projects, for instance how a gemstone can be shaped and cut.
It is also a very useful thing to know when it comes to your gemstone jewellery as it helps you to know how to store, even how to wear your jewellery pieces.
Why is the Mohs Scale Helpful?
It is extremely useful to know how hard a mineral is. From this we know, without having to experience the damaging results, that a diamond stored loosely next to a pearl could possibly scratch it and damage it.
A diamond is so strong that the only thing that will cut a diamond is another diamond. For this reason, diamonds are often used to cut glass or engrave on glass.
We have compiled a table below of some Precious and Semi-Precious Stones and Their Hardness (with links to relevant articles on each gemstone).
Gemstones & Mohs Hardness Score
| Gemstone (Alphabetically Arranged) | Mohs Hardness Scale Score | Gemstone (In Order of Hardness) | Mohs Hardness Score |
| Agate | 7 | Amber | 2 – 2 ½ |
| Alexandrite | 8 ½ | Copper | 2 ½ |
| Amber | 2 – 2 ½ | Gold | 2 ½ |
| Amethyst | 7 | Mother of Pearl | 2 ½ |
| Aventurine | 7 | Silver | 2 ½ |
| Aquamarine | 7 ½ – 8 | Copper | 2 ½ – 3 |
| Calcite | 3 | Jet | 2 ½ – 4 |
| Carnelian | 7 ½ – 8 | Pearl | 2 ½ – 4 ½ |
| Chalcedony | 6 ½ – 7 | Calcite | 3 |
| Citrine | 7 | Coral | 3 |
| Copper | 2 ½ – 3 | Malachite | 3 ½ – 4 |
| Coral | 3 – 4 | Steel | 4 – 4 ½ |
| Corundum | 9 | Flourite | 4 |
| Cubic Zirconia (CZ) | 9 | Turquoise | 4 – 6 |
| Diamond | 10 | Lapis Lazuli | 5 – 6 |
| Emerald | 7 ½ – 8 | Opal | 5 – 6 ½ |
| Fire Opal | 6 – 6 ½ | Hematite | 5 ½ – 6 ½ |
| Flourite | 4 | Fire Opal | 5 ½ – 6 ½ |
| Garnet | 6 ½ – 7 ½ | Chelcedony | 6 ½ – 7 |
| Gold | 2 ½ | Onyx | 6 ½ – 7 |
| Hematite | 5 ½ – 6 ½ | Peridot | 6 ½ – 7 |
| Jadeite | 6 ½ – 7 ½ | Agate | 7 |
| Jet | 2 ½ – 4 | Amethyst | 7 |
| Labadorite | 6 ½ -7 ½ | Aventurine | 7 |
| Quartz | 7 | Citrine | 7 |
| Lapis Lazuli | 7 or 5 – 5 ½ | Quartz | 7 |
| Malachite | 3 ½ – 4 | Rock Crystal | 7 |
| Moissonite | 9 ½ | Tigers Eye | 7 |
| Moonstone | 6 ½ – 7 ½ | Garnet | 6 ½ – 7 ½ |
| Mother of Pearl | 2 ½ | Jadeite | 6 ½ – 7 ½ |
| Rock Crystal | 7 | Labradorite | 6 ½ – 7 ½ |
| Ruby | 9 | Moonstone | 6 ½ – 7 ½ |
| Sapphire | 9 | Zircon | 6 ½ – 7 ½ |
| Onyx | 6 ½ – 7 | Aquamarine | 7 ½ – 8 |
| Opal | 6 – 7 or 5 ½ – 6 ½ | Carnelian | 7 ½ – 8 |
| Pearl | 2 ½ – 4 ½ | Emerald | 7 ½ – 8 |
| Peridot | 6 ½ – 7 | Tourmaline | 7 ½ – 8 |
| Silver | 2 ½ | Spinel | 8 |
| Spinel | 8 | Topaz | 8 |
| Steel | 4 – 4 ½ | Alexandrite | 8 ½ |
| Talc | 1 | Corundum | 9 |
| Tigers Eye | 7 | Cubic Zirconia (CZ) | 9 |
| Titanium Carbide | 9 – 9 ½ | Ruby | 9 |
| Topaz | 8 | Sapphire | 9 |
| Tourmaline | 7 ½ – 8 | Tungsten Carbide | 9 |
| Tungsten Carbide | 9 | Titanium Carbide | 9 – 9 ½ |
| Turquoise | 5 – 6 | Moissonite | 9 ½ |
| Zircon | 6 ½ – 7 ½ | Diamond | 10 |
The Mohs Scale Used on Everyday Materials
For most people it will help to reference the actual hardness of the gemstones they love and know so well by comparing them to everyday objects.
| Material | Scale of Hardness |
| Finger Nail | 2 ½ |
| Copper Penny | 2 ½ |
| Tooth | 5 |
| Pocket Knife Blade | 5.1 |
| Steel Blade | 6 ½ |
| Porcelain | 7 ½ |
| Sandpaper (covered in corundum) | 9 |
To Sum Up …
We hope this has explained what the Mohs Hardness Scale is and allows you to relate to it more when we talk about the hardness of different precious and semi-precious stones in our articles. We hope we’ve also highlighted what a valuable contribution this brilliant little Scale was to science, created way back in 1812 by Friedrich Mohs.
Sources
https://gizmodo.com/the-mohs-scale-covers-everything-from-diamonds-to-doubl-1688506986
