Are Diamonds Unbreakable? Hardness and Chipping

"A diamond is forever" is a nice line, but diamonds are not indestructible. Understanding why helps you protect your jewellery.

Hardness: what diamonds are very good at

Hardness is resistance to scratching. On the Mohs scale, which ranks minerals from 1 to 10 by what can scratch what, diamond is a 10. Nothing natural scratches a diamond except another diamond. That is why diamonds keep their polish for generations.

Toughness: where diamonds are weaker

Toughness is resistance to breaking or chipping when struck. A diamond's atoms are arranged in a way that gives it directions along which it can split, called cleavage planes. A hard hit at the wrong angle, especially on an edge or a corner, can chip or even split a stone.

So diamond is extremely hard but only moderately tough. Hardness and toughness are different properties.

Where do diamonds chip?

• At the girdle: the thin edge is the most exposed part.
• At corners and points: princess corners, pear tips and marquise points.
• At feathers: a fracture inside the stone can extend if struck.

Most chips are small and happen when a ring is knocked against a hard surface such as a counter, a doorframe or a car door.

How to reduce the risk

1. Take rings off for heavy work: gardening, gym weights, cleaning and carrying loads.
2. Choose a protective setting: bezels and sturdy prongs protect the girdle and corners. See diamond ring settings.
3. Choose a durable shape for daily wear: rounds and cushions without sharp corners.
4. Store pieces separately: a diamond can scratch other diamonds and other jewellery. See how to store diamond and gold jewellery.
5. Have prongs checked: loose prongs let a stone move and get knocked.

What if a diamond chips?

A small chip at the girdle can often be polished out by a skilled cutter, with a tiny loss of weight. A larger chip may call for recutting. Take the piece to a jeweller for assessment. See resizing and repairing rings.

Does a scratch on diamond jewellery mean the diamond is damaged?

Usually the scratches you see are on the metal, which is much softer than diamond. A cloudy look is more often dirt than damage. See why a diamond looks cloudy and how to fix it.

Thermal shock and chemicals

Diamonds withstand heat in normal life, but sudden extreme temperature changes can affect stones with fractures. Chemicals such as chlorine bleach do not harm diamonds but can damage the metal. See jewellery and water: bathing, swimming and the gym.

Wearing diamonds every day

With reasonable care, diamonds are among the most practical gemstones for daily wear. See can you wear diamond jewellery every day?.

Myths worth retiring

"A real diamond cannot be damaged." It can, as above, though it is hard to scratch.

"You can smash a diamond with a hammer to test it." Do not. A diamond can shatter under a hard blow, which is a quick way to destroy a good stone.

"Diamonds only chip in cheap jewellery." Chips are about handling and design, not price. A fine diamond in a vulnerable setting is as exposed as any other.

Get a safe setting

If you plan to wear a ring daily, ask about protective settings. You can browse diamond rings and book a visit to discuss which designs suit an active routine.