The Mohs Scale – A List of Gemstone Hardness


It’s often said that there’s nothing harder than a diamond, and we are often asked if a diamond is used to cut another diamond (the answer is yes)… But have you ever wondered how we know this? The answer is simple – the Mohs scale of hardness.

In 1812, Friedrich Mohs – famous geologist and mineralogist created a scale of mineral hardness grading from the softest (1) to the hardest (10). The scale was created using the simple technique of one mineral’s ability to visibly scratch another.

The softest mineral that features on the scale is Talc at 1, and everyday objects of hardness such as pencil lead (1.5), finger nails (2.5) and window glass (5.5) can help you get a true value of the scale.

We’ve taken a list of some of the most popular gemstones that are used in jewellery (some of which you’ll find on our website) to help you see the hardness of your favourite.

Gem Hardness
Diamond 10
Ruby 9
Sapphire 9
Chrysoberyl 8.5
Topaz 8
Spinel 8
Emerald 7.5 – 8
Aquamarine 7.5 – 8
Morganite 7.5 – 8
Amethyst 7
Quartz 7
Tourmaline 7 – 7.5
Citrine 7
Tanzanite 6.5 – 7
Peridot 6.5 – 7
Jasper 6.5 – 7
Tiger’s Eye 6.5 – 7
Zircon 6.5 – 7.5
Bloodstone 6.5 – 7
Onyx 6.5 – 7
Moonstone 6 – 6.5
Opal 5.5 – 6.5
Lapis Lazuli 5 – 6
Turquoise 5 – 6
Malachite 3.5 – 4
Coral 3 – 4
Pearl 2.5 – 4.5
Amber 2 – 2.5

Whilst this scale is a guide to mineral hardness, it does not always factor in other elements of a gemstones structure when you are considering stones for day to day wear. Emeralds for example are well documented as having many inclusions within the stone, these can often weaken the structure and make them more susceptible to scratching and even chipping – and some styles are not suitable for everyday wear. Citrines, however, are not recommended to come into contact with heat as they can fracture.

Diamond Gemstone Ring Ruby Gemstone Ring Sapphire Gemstone Ring Emerald Gemstone Ring Citrine Gemstone Ring
Diamond Ruby Sapphire Emerald Citrine
10 9 9 7.5 7

Caution and care should always be taken when wearing any gemstone jewellery so that these timeless beauties can be passed on for a lifetime. For more information about how to clean and care for your jewellery then do take a look at our cleaning guide here.

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