The Mohs Scale – A List of Gemstone Hardness

It’s often said that there’s nothing harder than a diamond – and people often ask if a diamond is used to cut another diamond (the answer is yes). But how do we know this?

The answer lies in the Mohs scale of hardness.

In 1812, German geologist Friedrich Mohs created a system to measure mineral hardness. The Mohs scale ranks minerals from 1 (softest) to 10 (hardest), using the simple test of one mineral’s ability to scratch another. This scale remains one of the most widely used methods for comparing gemstones and minerals today.

To put the scale into perspective, everyday items can also be measured. For example:

• Pencil lead – 1.5
• Fingernail – 2.5
• Window glass – 5.5

At the very top of the scale sits the Diamond (10), the hardest natural material known to man. At the bottom is Talc (1), which is soft enough to crumble in your fingers.

While the Mohs scale is a helpful guide, hardness alone doesn’t tell the full story. Other factors, like inclusions and crystal structure, can affect how durable a gemstone is in everyday wear. For example:

• Emeralds – Score 7.5–8 but often contain inclusions (“jardin”), making them more prone to chipping. An emerald and diamond ring is beautiful but may need extra care.
• Sapphires – With a hardness of 9, sapphire rings are excellent for daily wear thanks to their strength and durability.
• Citrine – Relatively durable at 7, but sensitive to heat. Rings with Citrine should be kept away from high temperatures to avoid fractures.

Gemstone shape and setting also play a role. Popular styles such as emerald cut diamond rings and radiant cut engagement rings not only showcase brilliance but can also provide added protection to stone edges.

We’ve highlighted some of the most popular gemstones used in jewellery in our Gemstone Rings collection. This list shows where your favourite gemstones sit on the Mohs scale and helps you understand their durability.

The Mohs scale of hardness is an essential guide to understanding gemstone strength. While Diamond is unmatched at 10, every gemstone has its own qualities that influence how suitable it is for everyday wear. Whether you’re choosing a practical ring or a statement piece, knowing where a stone sits on the scale can help you pick the perfect design. Explore our full gemstone rings collection to find jewellery that balances beauty, symbolism, and durability.