Understanding the Mohs Hardness Scale for Gemstones

The gemstone hardness scale is one of the most important factors to understand when choosing jewellery. 

The Mohs hardness scale for gemstones system essentially measures how resistant a stone is to scratching, helping you determine which gemstones are suitable for everyday wear. 

So, at GS Diamonds we thought we’d give you a go-to guide regarding the Mohs scale, how it works, and why it matters when selecting pieces like engagement rings. No more guessing!

What does gemstone hardness mean in gemology?

In gemology, “hardness” refers specifically to a gemstone’s resistance to scratching, not its toughness or durability overall.

This means:

• A harder gemstone is less likely to scratch
• A softer gemstone may show wear over time

Understanding the gemstones’ scale of hardness helps you choose stones that maintain their appearance, especially in jewellery worn daily.

What is the Mohs hardness scale and how does it work?

The gemstone Mohs hardness scale system ranks minerals from 1 to 10 based on their ability to scratch one another.

• 1 = very soft (e.g. talc)
• 10 = hardest (diamond)

Each level can scratch the one below it, but not above.

For example:

• Sapphire (9) can scratch topaz (8)
• Diamond (10) can scratch all other gemstones (as it’s the hardest and most resilient natural material on Earth)

This scale to measure the hardness of gemstones is widely used in both jewellery design and gemstone selection.

Mohs scale of hardness chart

Here’s a simplified gemstone hardness scale chart for you, so you can remember the rating of each one of the most popular gems:

What does gemstone wearability mean?

Hardness directly affects wearability, especially for rings.

• 8–10 Mohs → Suitable for everyday wear (engagement rings)
• 6–7 Mohs → Suitable for occasional wear
• Below 6 → Better for earrings or pendants

This is why diamonds are the most popular choice for engagement rings, offering unmatched scratch resistance. You can explore loose diamond options in our stunning diamonds collection.

Gemstone hardness scale for engagement rings

When choosing a gemstone for an engagement ring, hardness matters more than almost any other factor.

A gemstone hardness scale for engagement ring selection should prioritise:

• Minimum hardness of 8 for daily wear
• Resistance to scratches from dust (which contains quartz at level 7)
• Long-term durability

For this reason:

• Diamonds (10) → best for daily wear
• Sapphires & rubies (9) → excellent alternatives
• Emeralds (7.5–8) → require a bit more care

If you're comparing alternatives, our guide to the best gemstones for engagement rings breaks down durability and suitability further.

How to test mineral hardness

In professional settings, hardness is tested using scratch testing, comparing one material against another. At home, this is not recommended for finished jewellery, as it can damage the stone or setting.

Instead you should:

• Rely on certified gemstone information
• Consult a jeweller for accurate evaluation

Why the gemstone hardness scale matters

The Mohs gemstone hardness scale is more than a technical concept, as it directly impacts how your jewellery looks and wears over time.

Choosing the right hardness level ensures your jewellery maintains its brilliance and structure, especially for pieces worn every day. 

At GS Diamonds, we can help you balance beauty with durability, so you can choose gemstones that not only look exceptional, but last for generations.