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), based on that information jewellers were searching for perfect the cut of a diamond. 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 – you’ll find many of them in our Gemstone Rings collection and more products available on the Purely Diamonds website. This list will help you see the hardness of your favourite.

Gemstone Hardness Scale

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 gemstone’s structure when you are considering stones for day-to-day wear. Emeralds for example are well documented as having many inclusions within the stone, that’s why a ring with emerald and diamonds is a special one. 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, otherwise, Sapphire Rings are excellent for everyday wearing because of the high hardness level. However, it depends on the stone shape. Some of the most popular types of gemstone jewellery products are Diamond Emerald Cut Rings and  Radiant Cut Engagement Rings. Rings with Citrines, however, are not recommended to come into contact with heat as they can fracture. Let’s view the following list for more details:

Popular Gemstone Rings and their Hardness

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 read our guides: