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Mohs Hardness Scale for Gemstones

The hardest and softest gemstones are...

As you probably already know, diamonds are the hardest substance on Earth, meaning that diamonds can scratch the surface of any other matter when in contact! On the other hand, as readers of the Laine Jewellery blog may remember, we have mentioned that pearls and mother-of-pearl are softer organic gemstones and could sustain abrasions more easily.

Gemstones have different levels of hardness. The “Mohs Hardness Scale” is a commonly used method in mineralogy and gemology to identify relative hardness. Developed by German geologist and mineralogist Friedrich Mohs in 1812, the Mohs Hardness Scale is a qualitative ordinal scale that characterises a mineral’s hardness in relation to other minerals but does not illustrate the absolute hardness.

The Mohs Hardness Scale describes the hardness of common minerals on a scale of 1 to 10, the larger the number, the harder the mineral, i.e. 10 being the hardest and 1 being the softest. Naturally, the hardest gemstone would be diamonds, while next would be gemstones from the corundum family (e.g. sapphires and rubies), which are the hardest known natural substances after diamonds. At the other end of the spectrum, talc is the softest mineral and is assigned to number 1. If a mineral’s hardness falls between two numbers, it can be described with .5. Let’s have a look at the hardness of different gemstones!

It would be hard to gauge actually how hard a gemstone is simply based on the relative numbers on the Mohs Scale. Here are the Mohs hardness levels of various daily objects to give you a better picture:

Masonry drill bit (for drilling tiles and concrete) 8.5 - 9

Steel nail 6.5

Glass 5.5

Copper coin 3.5

Fingernail 2.5

The hardness of gemstones is a useful reference. On the one hand, it reflects the wearability of gemstones. The harder a gemstone, the more scratch-resistant it is; while softer gemstones, such as pearls, would require more care and attention.

On the other hand, harder gemstones would achieve a better outcome and sparkle after cutting. This is the reason why diamonds, sapphires and rubies tend to have a more intense sparkle. Then of course, a good cut is needed to have the best results.

Feel free to get in touch with Laine Jewellery for recommendations and advice on diamonds or customised rings! I offer free consultation services every Friday at my studio at Two ifc, bookings required. Interested parties please make a reservation through Whatsapp or Laine Jewellery’s Facebook page!

Whatsapp: +852 6819 2038


Elaine 💌


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