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Determining Rank on the Mohs Scale of Mineral Hardness
Monday, May 11, 2015

Whether you’re young or old, it’s pretty much common knowledge that diamonds are one of the hardest known natural materials (if not the hardest) on Earth. But how did diamonds receive this ranking? It wasn’t arbitrary; there is a scale in place that measures the hardness of minerals. Known as the Mohs scale of mineral hardness, this scale was named after the German mineralogist who determined the hardness of 10 minerals, Frederich Mohs.

This particular scale characterizes the scratch resistance of several minerals through the ability of a harder material to scratch a softer material. The scale ranks minerals on a range of 1 to 10, with 1 being the softest and 10 being the hardest. As you may have already guessed, a diamond tops the scale with a ranking of 10, while talc graces the bottom of the scale of currently being the softest.

But where do other minerals fall on the scale? What do these middle numbers get? Minerals that are mined, common minerals, gemstones, and numerous other minerals have been included on the Mohs scale over the years since Frederich Mohs devised it in 1812. Here we’re listing a few well-known minerals and where they rank on the Mohs scale of hardness.

·      Graphite
While diamonds top the scale at 10, their carbon counterpart, in the form of graphite, come in pretty low on the Mohs scale of mineral hardness. Graphite only ranks a 1 to 2. No wonder number 2 pencils break so easily!

·      Gold
With various karats of gold jewelry on the market, and pure gold being too soft to use in jewelry, it doesn’t surprise us that gold ranks pretty low on the Mohs scale. Gold clocks in between the ranks of 2.5 to 3. If you’ve ever wondered why your 24 karat gold engagement ring has been molded to the shaped of your finger, you now have your answer: this metal falls on the softer side of the hardness scale of minerals.

·      Silver
As we covered one popular metal used in jewelry, we felt it was only logical to share with you silver’s ranking on the Mohs scale as well. Though it may not be as popular as gold, silver doesn’t hold its own in this battle; the grayish metal also ranks a 2.5 to 3 on the Mohs scale of mineral hardness. It looks like we humans just enjoy soft metals to be used in jewelry.

·      Garnet
January’s birthstone is known for its deep, blood red color, and we felt we had to share its hardness ranking with you. The garnet is one of a few minerals that are a part of a solid solution series where they can change in hardness as the composition varies. Because of this, garnets can rank anywhere on the Mohs scale of hardness from a 6.5 to an 8. With the majority of minerals only having a 0.5 difference, this means the garnet can range from anywhere to relatively soft to almost solid … solid as a rock.

·      Zircon
Not to be confused with cubic zirconia, the imitation stone that acts as a stand-in for diamonds that is also laboratory-grown, zircon is actually a naturally occurring gem. Zircon comes in a variety of colors such as blue, green, red, orange, pink, purple, yellow, white, and colorless, with the most common color being brown. Blue zircon is actually considered an alternative birthstone for December. But as the stone often gets confused for cubic zirconia, don’t get it confused with a diamond! Zircon has a double reflection, which gives it a much “fuzzier” appearance than a diamond. But in keeping up with the diamond fashion, zircon does rank relatively high on the Mohs scale of mineral hardness. This gem gets a whopping 7.5.



Since Mohs created this hardness scale in 1812, many scientists and mineralogists have relied on it and even discovered the hardness ranking of other minerals and gems. Whether you’ve realized it or not, the Mohs scale of mineral hardness has had an effect on your life with so many minerals being used in everyday applications. And on a scale of 1 to 10 — or should we say talc to diamond? — how frequently do you use this scale without even knowing it?



 
 
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