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The Mohs' Scale
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| Hardness | Mineral |
| 1 | Talc |
| 2 | Gypsum |
| 3 | Calcite |
| 4 | Fluorite |
| 5 | Apatite |
| 6 | Orthoclase Feldspar |
| 7 | Quartz |
| 8 | Topaz, Emerald, Aquamarine |
| 9 | Corundum (Ruby, Sapphire - twice as hard as Topaz) |
| 10 | Diamond (four times as hard as Corundum) |
According to the scale above, the softest material is Talc (which can be scratched with a fingernail), while the hardest is Diamond. So, what does this mean in the real world?
A mineral with a Mohs' hardness of 7 will scratch any mineral of the same hardness or less, but can be scratched itself by a mineral with the same or higher number. Diamond, having the highest number, is the hardest gem known to man, and is used not only for beautiful jewelry, but also in many industrial applications because of its durability.
The most valuable gems have a hardness of 7 or more. Most highly prized gemstones are also the hardest, like diamond, ruby, sapphire or emerald. Usually anything below a hardness of 7 is liable to be damaged quickly in everyday wear in jewelry.
To give you some idea of the hardness of every day things, a fingernail has a Mohs' hardness of 2.5, a penny is 3, a knife blade or fragment of window glass is 5.5 - 6, while a small piece of emery cloth is between 8 and 9.
The Mohs' scale is important to jewelers and bead artists for many reasons. It's important to know the hardness of a stone or bead before you make a piece of jewelry with it. Putting a soft stone bead next to a hard stone bead can cause damage to the finished piece. Whan making jewelry with softer faceted stones or cabs, it's important to protect the stone as best as possible to minimize wear.
If you want to learn more about the Mohs' scale of hardness and various rocks and minerals, a great resource is "The Audubon Field Guide to North American Rocks and Minerals".
Author Mary Harvey owns Custom Jewelry Supply, supplies for jewelry designers and wire artists. Her biweekly newsletter, The Jewelry Crafter, is full of useful information for your jewelry business - you can subscribe to it on the main page of her site, near the bottom of the navigation column at the left.
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