Type I (Ia, Ib) and Type II (IIa, IIb) Diamonds: An Expert Guide

So, you’ve heard about the 4Cs right? Cut, color, clarity and carat. You know everything there is to know about this grading system and just when you think you’ve read it all…we go and start talking about DIAMOND TYPES.

There are a few different ways to classify a diamond and it would be rude to not discuss the diamond types here today. Whilst it’s arguable that this isn’t knowledge that you need in order to make an informed buying decision…the more knowledge you have, the better!😉

So today we’re going to run you through the ins and outs of Type I and Type II diamonds. In short, diamond type refers to the classification of a diamond based on its color and physical properties at an ATOMIC level (oh yeah, it’s going to get scientific over here).

Here we go!

Different Diamond Types

How are diamonds formed and what is their composition?

Before we dive into the good stuff, it’s worth taking a hot moment to recap over the formation process and the composition of diamonds.

We need to know exactly what it is we’re dealing with here, right?!

Now, a common misconception that many people believe is that diamonds form from coal. Take it from us, this is not the case! Contrary to this popular belief, coal rarely—next to never in fact—plays a role in the diamond formation process.

For the purpose of this article, we won’t dive into each of the different processing types. Here’s the most important, juicy stuff worth knowing about the formation process…

Under extreme pressure and heat beneath the earth’s surface, carbon atoms crystallize to form DIAMONDS. The lattice arrangement of the single carbon element is what gives the diamond its stunning properties.

Let’s quickly talk about IMPURITIES.

Any other substance found in the chemical makeup of a diamond that is not carbon, can be considered an impurity.

These impurities are often called "nature’s birthmarks" which have a poetic and romantic appeal, don’t you think?😎 And this is because these impurities become present during the formation process (so whilst every diamond is unique, so are its impurities!).

The most commonly found impurities tend to be atoms of nitrogen or boron. And these are what we will be focussing on today!✍🏻

What are the different diamond types?

Firstly, what do we mean when we talk about diamond type? Well, we’re glad you asked!

Diamond type is a method of scientifically classifying diamonds by the level and type of their chemical impurities.

Unlike inclusions, these chemical impurities are measured at an atomic level (meaning deep within the crystalline carbon atom structures) and so they require specialist equipment to detect because…the naked eye simply won’t do! But more on that in a short tick!

Now, you may have come across some common classification methods that feel more familiar. Let’s take a look at those…

Different diamond classification methods

Okay, so we’re going to go all-in on Type I and Type II today but here are two other classifications that you may have considered before when trying to distinguish what type of diamond you are buying…

Natural diamonds vs. Non-natural diamonds

Now, the natural diamonds are the dazzling beauty that arises from the earth after many years of forming under extreme heat and pressure. These little beauties are the ones we mentioned earlier, remember?

The natural diamond is formed of only carbon atoms whereby any other chemical element found is considered an impurity. This is the natural diamond.

A non-natural diamond on the other hand is exactly what it says on the tin! A diamond that is not naturally formed. Terms that may be used to describe these non-natural diamonds might include "man-made" or "synthetic diamonds" or "lab-grown".

These are created in a controlled environment to mimic the beauty of a natural diamond. And indeed, they can do a fantastic job! They can be created with next to no impurities because of the strict conditions under which they are formed.

(However, many people call these "fake diamonds"  because they are not natural and of course, can be purchased at a lower price because of this)

Colorless diamonds vs. Colored diamonds

Colorless diamonds is the term used for what we typically know to be a diamond. In this sense, in colorless diamonds, we are looking for an absence of color. The brighter, whiter and clearer a colorless diamond can be oftentimes the best!

When we do see color within a colorless diamond it tends to appear in yellowish/brownish tones. Some people enjoy the warm tonality of these stones but the finest white diamonds demand a higher price!

Alternatively, colored diamonds are often termed Fancy Colored Diamonds. Fancy-colored diamonds come in almost any color you could dare to dream of!

From blue, pink, orange, purple, black and green…It really is a rainbow selection of color to choose from where fancy colored diamonds are concerned. We’re often looking for depth of color and an even tone when seeking a valuable fancy colored diamond.

(But as with all things, personal taste has a huge part to play!)

How are we determining diamond type?

Before we continue, we want to make sure that everything is crystal clear (because things can get technical!)...

The diamond types in this article are determined based on the presence or absence of specific nitrogen impurities. This is then further subdivided in relation to the arrangement of these nitrogen atoms alongside the presence of boron impurities.

Now, with that said, let’s get going!

Atom Structures of Different Diamond Types
Source: North Arrow Minerals Inc.

Type I Diamonds

Type I diamonds are considered the most common class of diamond and contain nitrogen atoms as the main impurity source.

Type Ia

The vast majority of all natural diamonds are Type Ia diamonds. Up to 95% of all natural diamonds are on the market in fact! (So perhaps this is the most important type to be aware of!)😎

The nitrogen impurities within the carbon lattice appear throughout the stone. They tend to range from near-colorless to a light yellowish tone (which is the presence of nitrogen!).

This is where we can subdivide Type Ia diamonds into three further categories:

  • Type IaA - This type of diamond contains nitrogen atoms that appear in pairs (known as A-aggregates) and these do not affect the color of the diamond.
  • Type IaB - This type of diamond contains nitrogen atoms that appear in clusters of four (called B-aggregates), and the color of this type of diamond is not affected as well.
  • Type IaN3 - In this diamond type, nitrogen occurs in groupings of three which would lead to a yellow color in the diamond.

Type Ib

As opposed to the cluster formation of nitrogen atoms in the Type Ia diamonds, the Type Ib diamonds contain isolated nitrogen atoms in a singular form.

This type of diamond is far more rare than the Type Ia diamonds. They consist for only 0.1% of all natural colored diamonds compared to the whopping 95% of Type Ia!😱

Both green and blue light are often absorbed with these diamonds and the diamond color can be INTENSE and so these types often account for the fancy colored diamonds with their luscious colors.

That is why, in the marketplace, Type Ib diamonds tend to make up most of the fancy colored diamonds out there with their fantastic display of color!🌈

Type II Diamonds

Alright, that’s Type I covered, let’s take a look at the two subcategories for Type II diamonds…

Type IIa

If there is one type of diamond where you will not find any measure of nitrogen or boron, it’s Type IIa! This diamond type makes up only 1% all all naturally mined diamonds.

If you’re searching for the most chemically pure diamond, this is the type to go for (if you can get your hands on any that is!). They are incredibly sought after by investors and diamond fanatics for that very reason.

You may sometimes hear that these rare beauties go by the name of "Golconda Diamonds" known for their exquisite D color, high clarity ratings and lack of fluorescence.

Cullinan and Koh-I-Noor are the names of two of the world's most famous diamonds and, you’ll never guess what…they are classed as Type IIa!

Type IIb

Last but by no means least is the Type IIb diamonds. Incredibly rare and incredibly stunning, they make up for only 0.1% of all natural diamonds. And the diamonds that have the pleasure of belonging to this category do not contain any nitrogen but instead they contain boron impurities within the stones composition.

The presence of boron often results in a blue-ish, gray-ish hue which again, is incredibly sought after by collectors.

The Hope Diamond is considered THE MOST FAMOUS DIAMOND IN THE WORLD (talk about that for a title) and at 45.54 carats this absolute beauty is indeed a Type IIb!

How is the knowledge of diamond type used by gemologists and customers?

I know you’re wondering, "Do I really need to know all of this?"

Well, it never hurts to have more information than necessary, especially when you’re investing in something as special as a diamond. But this information is used differently for gemologists and customers…

The significance of diamond type for gemologists

Where gemologists are concerned, knowledge of diamond type allows them to identify whether or not a diamond is natural, synthetic or treated. (today most lab-grown diamonds are Type IIa)

Using this information, they can consider whether the diamond should be sent for further testing. Simple!

The significance of diamond type for customers

Now, let’s be real for a moment…

The truth is, with 95% of all natural diamonds being Type I there’s really no real reason as to why a customer would need to worry themselves too much about whether they have type I or type II (because you likely have type I!).

But…at auction or in case of investment, it’s crucial to confirm the diamond type because as we have now learned, Type II diamonds are incredibly rare and that will make a HUGE difference to the value of your investment!

How to detect or know the type of diamond?

If we’re talking about identifying impurities at an ATOMIC level, how are we to know?! Those eye loops aren’t going to do much good.🤓

Let’s break it down…

How geologists detect diamond type

For gemologists, a Fourier transform infrared spectrometer (FTIR) is used…try saying that ten times as fast as you can!

During inspection, the diamond is wrapped in putty to act as a barrier to all outside light that may affect the results.  A small hole is left at the base of the putty to allow the diamond to reflect light. It is then placed under the infrared spectrometer under incredibly strong (and quite dangerous!) UV light which allows the spectator to observe the chemical structure of the diamond at an atomic level.

How customers detect diamond type

For us customers, things are a lot simpler!

The GIA has got us covered and can offer a Diamond Type Analysis as a supplemental service to the GIA diamond grading reports.

Now, with Type I diamonds being so incredibly common, it is not often considered necessary to acquire such a report for these particular stones (the 4Cs grading system generally does the trick!).

However, with Type II diamonds being so rare, jewelers generally get a Diamond Type Analysis for these particular stones.

Is it possible to have a diamond that consists of both Type I and Type II?

Exciting as it would be to round this all off with some super awesome hybrid of both Type I and Type II diamonds, I'm afraid that’s just not the case.

The diamonds we have the pleasure of receiving from the earth are always categorized as either Type I or Type II. Thank you for keeping it simple mother nature.

However, non-natural diamonds that are synthetically created in a lab can be created in any way the manufacturer requires. So, whilst they haven’t done so just yet, they could (in theory) decide one day to create a diamond that is an amalgamation of the two types…and that will be an interesting day indeed!

Does Diamond Type Really Matter?

As with anything, context is EVERYTHING.⚠️

With most naturally formed diamonds making up for a whopping 95% of the marketplace it would be easy to argue that no, it really doesn’t matter.

However, as mentioned, if you are looking for a juicy investment or buying at auction then it will certainly pay off to know if you’ve got a rare Type II in your midsts! For most of us, the 4Cs grading system really is good enough to allow us to make an informed decision about our diamond purchase.

While diamond type correlates to color, the 4Cs give us a more practical and accessible approach.

(So maybe Diamond Type can be left to the real fanatics!)

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