The short answer: cleavage is a direction in which a gem can split cleanly when struck, which makes stones with strong cleavage, such as some tanzanite, kunzite and topaz, more prone to chips. Choose a protective setting and take care with these stones.
Hardness tells you about scratches. Cleavage tells you about a different risk, which is chipping or splitting when a stone is knocked.
What cleavage means
Some crystals have planes where the bonds between atoms are weaker. A sharp knock along that plane can cause a clean break or chip. Diamond has cleavage too, which is why cutters take great care with it, but its overall toughness is high.
Hardness, toughness and cleavage
Three words often get mixed up. Hardness is resistance to scratching, toughness is resistance to breaking, and cleavage is the tendency to split along a particular direction. A stone can score well on one and badly on another, which is why a very hard stone can still chip. When we advise on a setting we look at all three, along with the shape of the stone and how you plan to wear it.
Examples
| Stone | Cleavage risk |
|---|---|
| Diamond | Present, but very tough in practice |
| Sapphire and ruby | No true cleavage, though they can part along weak planes |
| Emerald | Fragile because of inclusions |
| Tanzanite | Cleavage present, so it needs care |
| Kunzite | Strong cleavage |
| Topaz | Strong cleavage |
This is a general guide, and individual stones vary.
Protecting a stone
- Use a bezel or a halo to cover the edges.
- Avoid sharp pointed corners where possible, or protect them with V claws.
- Remove the ring for sport, gardening and heavy work.
- Have the setting checked regularly.
Chips come from corners and edges
Most chips start at a corner, a point or a thin edge, where a knock concentrates force. That is why pear, marquise, princess and step cut stones need extra care. See our guides to protecting the corners of step cut stones and pear shaped settings.
Choosing a setting for a delicate stone
If you love a stone that is prone to chipping, you do not have to give it up. A bezel gives the strongest protection, a halo adds a buffer of metal and small stones, and a low setting keeps the stone out of harm's way. A stone that is going to be worn daily needs a more protective design than a stone for an occasional ring or a pendant. Tell us how you will wear it and we will recommend options, then show them in a CAD render.
If a stone chips
Chips can sometimes be polished out or the stone recut, but this can reduce size. Talk to your jeweller early.
Everyday habits that help
- Put the ring on last and take it off first.
- Do not use a ring as a tool, for example to open a packet.
- Store each piece separately so stones do not knock together.
How to choose
- Check whether your stone has cleavage.
- Pick a protective setting.
- Decide how you will wear it.
See the hardness chart, kunzite and best settings for emerald. Nothing is made until you approve the design in writing, and our standard making time is 5 to 6 weeks, which can vary with your location and how busy we are. Pieces start from £600.
Frequently asked questions
Is cleavage the same as hardness? No, they are different properties.
Can I wear tanzanite daily? With care and a protective setting.
Do diamonds chip? They can, though they are very tough.
Can a chip be repaired? Sometimes, by polishing or recutting, which may reduce the size.