Can Gemstones Break? Understanding the Difference Between Hardness and Toughness

Quick Answer

“The gemstone is hard, so it won’t break” — this thinking is completely wrong. Hardness and toughness are two different properties. Hardness tells you how easily a gemstone can be scratched, while toughness tells you how well it resists breaking, chipping, or fracturing from impact or pressure. Topaz’s (Mohs 8) perfect cleavage and emerald’s (Mohs 7.5–8) natural fractures are both good examples of how high hardness is no guarantee of full protection against breaking.

Introduction

When buying a gemstone, people often look only at hardness (the number on the Mohs scale) and assume that the harder the gemstone, the stronger and safer it is. That’s only half the truth. Hardness only tells you how well the gemstone’s surface resists scratching — it’s no guarantee that the gemstone won’t break under a direct blow, a fall, or pressure. In this guide, we’ll understand the difference between hardness and toughness through examples, and explain how to protect gemstone jewellery from impact and fracturing in everyday life.

Hardness vs. Toughness — What’s the Difference

• Hardness: This measures how easily a gemstone’s surface can be scratched. It’s measured on the Mohs scale — the higher the number, the greater the resistance to scratching.
• Toughness: This measures how well a gemstone resists breaking, chipping, or fracturing from impact, pressure, or a knock.

A gemstone can rank high in hardness and still be weak in toughness — which is why “hard” gemstones can still chip or break easily if not handled carefully.

Example: Topaz and Emerald

Topaz has a hardness of Mohs 8, which is considered quite good. But topaz has a special property — perfect cleavage, meaning its internal structure has a clear plane along which it can split cleanly with a single sharp blow. Despite its high hardness, this property makes topaz sensitive to impact in that particular direction.

Emerald also has decent hardness (Mohs 7.5–8), but the natural inclusions almost always present in it make the gemstone prone to fracturing under pressure or impact. In other words, despite a good-looking hardness number, emerald is actually counted among the most delicate gemstones.

Both these examples make it clear — hardness alone can’t tell you how strong a gemstone is overall.

What to Do for Safety

1. Remove your ring and other gemstone jewellery before heavy physical work, sports, or any activity where there’s a risk of impact or a blow to the hand.
2. Avoid sudden temperature changes — such as keeping a ring on in cold air right after bathing with hot water.
3. Periodically have a jeweller check the strength of the setting and prongs, so a loose setting doesn’t put the gemstone at additional risk of impact.
4. Handle gemstone jewellery with care, especially gemstones that have properties like cleavage or natural fractures.

What to Avoid

• Thinking “it’s hard, so it’s safe”: Don’t forget that hardness and toughness are different properties.
• Wearing jewellery during heavy work or sports: Direct risk of impact and blows.
• Sudden temperature changes: Going abruptly from heat to cold (or cold to heat) while wearing a ring.
• Ignoring a loose setting: A weak setting puts the gemstone at additional risk.

Quick Facts

Gemstone	Hardness (Mohs)	Breakage-Related Weakness
Topaz	8	Perfect cleavage — can split with a single precise blow
Emerald	7.5–8	Risk of fracturing due to natural inclusions

Expert Tip: When buying or wearing a gemstone, don’t assume from the Mohs hardness number alone that it’s also safe from breaking. Every gemstone has its own internal structure — so removing jewellery during heavy work, sports, or sudden temperature changes is always the safest habit.

Buying Advice

When buying a gemstone, don’t focus on hardness alone — also understand its toughness and internal structure, so you can take the right precautions in everyday use. Be sure to also read our guides on cleaning emerald and the right way to store gemstones. For accurate information and quotations on certified gemstones, contact us.

Key Takeaways

• Hardness measures resistance to scratching, toughness measures resistance to breaking — they’re two different properties.
• Topaz’s (Mohs 8) perfect cleavage makes it sensitive to splitting with a single blow.
• Emerald’s (Mohs 7.5–8) natural fractures make it sensitive to fracturing.
• Protect jewellery from heavy work, sports, and sudden temperature changes, and have the setting checked regularly.

Conclusion

No matter how hard a gemstone is, it isn’t indestructible. By understanding the difference between hardness and toughness, and adopting a few everyday precautions — removing jewellery, avoiding temperature changes, getting the setting checked — you can significantly reduce the risk of your gemstones breaking or fracturing.