What is Cleavage in Diamonds and Gemstones?

​Even though diamonds are the hardest naturally occurring mineral, they are not indestructible. Hardness is just a measure of how easily a stone can be scratched. Diamonds have cleavage, and cleavage can make a diamond susceptible to fractures or chipping.  ​

What is Cleavage?  

Cleavage is the weakest plane in a gemstone where the gemstone can split. Cleavage is caused by weak atomic bonds. 

Diamonds have 4 perfect cleavage planes, meaning they can split into 4 different places. Gemstones can receive one of the following grades for cleavage:  

• None 

• Poor 

• Good 

• Indistinct 

• Excellent  

• Perfect 

​It’s possible for stones to not have any cleavage at all. Stones without cleavage include ruby, sapphire, alexandrite, opal, and turquoise.  

Why is Cleavage Important?  

Cleavage is important for gem cutters to take note of. Stones are easier for them to cleave, or split, along their cleavage planes. Additionally, the type of cleavage a stone has will determine how difficult it will be to cut. For example, stones with poor cleavage will leave behind rough surfaces when cleaved. Diamonds, on the other hand, will cleave easily and smoothly as they have perfect cleavage. 

Have you ever heard of toughness? Toughness is a gemstone’s ability to withstand chipping or breaking. It’s a big factor when it comes to determining how durable a stone is. Cleavage can affect a stone’s toughness and overall durability.  

Stones can receive one of the following ratings for toughness:  

• Poor 

• Fair 

• Good 

• Excellent 

Diamonds are considered to have a “good” rating when it comes to toughness since their cleavage makes them susceptible to breaking. But stones like sapphire or ruby have an “excellent” rating for toughness as they do not have cleavage, meaning they are more durable than diamonds.  

So, while it is possible for your diamond to break, it’s a rare occurrence and it would be pretty difficult. It’s still important to remove diamond jewelry, especially diamond rings, during strenuous activities to avoid chipping the stone.  

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Up Next: 9 Things You Should Be Doing to Take Care of Your Ring ​