What Are Type IIa Diamonds?

If you’ve recently purchased a lab grown diamond, you’ve hopefully taken a look at its grading report. A diamond’s grading report is an official document from an independent laboratory listing all of its qualities. 

Your diamond’s grading report may specify that your new stone is a Type IIa diamond – but what does this actually mean? Before we go into detail about Type IIa diamonds, let’s take a step back for a moment.

What are diamond types?

Diamond types are a scientific way of classifying diamonds based on their physical properties and color. Diamond types are important because they can help differentiate between a natural, lab-grown, and treated diamond.

There are Type I and Type II diamonds. Type I diamonds are the most common. These diamonds contain nitrogen as their main impurity, while Type II diamonds do not have measurable nitrogen impurities.

These categories are further broken down into Type Ia, Type Ib, Type IIa, and Type IIb.

What is a Type IIa Diamond?

Type IIa diamonds have no measurable nitrogen or boron impurities. They are the most chemically pure diamonds and have the highest thermal conductivity. Type IIa diamonds are often colorless or near-colorless. They can also be gray, light brown, light yellow, or light pink. Natural Type IIa are extremely rare – only 1-2% of earth-grown diamonds are Type IIa. However, most lab-grown diamonds are Type IIa. When diamonds are tested in a lab, a major indicator that they are lab-grown is when they test as a Type IIa diamond because they are so rare in nature.

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Famous Type IIa Diamonds

Earth-grown Type IIa diamonds are incredibly valuable because they are so rare. These natural diamonds are well known for their beauty and their large carat weights.

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The Elizabeth Taylor Diamond, also known as the Krupp Diamond, is a Type IIa Asscher cut diamond weighing 33.19 carats. It sold in 2011 for $8.8 million. 

 The world’s largest gem-quality rough diamond, The Cullinan Diamond, is a Type IIa diamond. The rough diamond weighed 3,106.75 carats. It was eventually cut into 9 large stones (above) and several smaller ones. Because the Cullinan Diamond was cut into separate pieces, it’s hard to say exactly how much it is worth, but when combined, all of the stones would be worth billions.

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The Pink Legacy diamond is a 18.96 carat fancy vivid pink diamond. This Type IIa diamond sold for $50.4 million in 2018.