Diamond connoisseurs are familiar with the 4Cs of diamond grading: Cut, Clarity, Colour and Carat weight. However, for the purist, there is another attribute that sets diamonds apart: diamond type. There are four main types of diamond: type 1a, type 1b, type 2a and type 2b. The most sought after is type 2a. This article describes the most highly prized of diamond types, the type 2a.

What Are The Different Diamond Types?

Until the 1930s, there was just one diamond type. We did not know that a diamond might have different forms because the differences occur at the atomic level and can only be discerned using specialised equipment.

Diamond is a crystalline form of the familiar black material, carbon. Under conditions of high temperature and pressure carbon atoms, which generally align in a flat, fragile, sheet-like form are forced into a very hard, crystalline structure. That crystalline structure is the diamond.

Some diamonds have different colours; these colours are due to impurities within the diamond giving colour to the ordinarily transparent crystals. The most common impurity, nitrogen gives diamonds the yellow tint that is graded in the GIA 4Cs system as colour.

Type 1a diamonds are those that carry nitrogen within the crystalline structure. The nitrogen atoms are found in clumps within the diamonds lattice crystal structure along with the carbon atoms making up the diamond. There are sub-types of 1a that depend upon the arrangement of the nitrogen atoms in the overall diamond structure.

Type 1a diamonds are the most common type of diamond amounting to approximately 98% of all diamond production.Type 1b diamonds are much less common, accounting for around 0.1% of all diamonds. In this form, the nitrogen is found as individual atoms in the lattice and give the diamond a very yellow colour called Canary Yellow Diamond.

Type 2b diamonds are also impure. In this case, the impurity is from atoms of boron, or sometimes hydrogen, locked into the atomic structure of the crystal. The boron or hydrogen, like nitrogen, gives the diamond a colouration. Boron gives a blue colour to the diamond which many buyers like to see.

Type 2a diamonds are the most prized of the types of diamond because unlike almost all other diamonds, this type is entirely pure. There is no nitrogen or boron in the lattice structure; the whole diamond crystal is 100% carbon.
Taken together type 2 diamonds amount to less than 2% of all diamonds found globally.

Type 2a Diamonds Explained

Type 2a diamonds being completely pure, are usually entirely colourless. Only around 1-2% of diamonds mined are type 2a. Type 2a diamonds are the essence of what most people see as being perfection in a diamond, large, brilliant, and clear white.

Although type 2a diamonds are rare, most of Australia’s diamond production is of type 2a stones.

Most type 2a diamonds are large, typically over 10 carats when uncut.

Golconda Diamonds

Type 2a diamonds are sometimes called 'Golconda Diamonds'. The name commemorates the Indian diamond mines that were the source of some of the world’s largest and most famous diamonds, such as the Koh-i-Noor, in the 16th and 17th centuries. These mines are now mined out. Diamonds from the region are among the clearest and most brilliant that have been found. Many of these stones are now known to be type 2a diamonds and are sought after by diamond collectors.

Type 2a Coloured Diamonds

Although most type 2a diamonds are entirely free of colour, some do have colours such as pink, blue, grey or brown. Unlike most diamonds where colouration is due to impurities; in the case of type 2a stones, the colour is created during the formation of the diamond in a process called plastic deformation. Plastic deformation occurs while the diamond is being forced toward the surface of the Earth and is a slight change in the lattice structure due to the intense pressures involved. The slight rearrangement of the atoms within the crystal causes the diamond to absorb specific frequencies of light, giving rise to colour in the crystal.

It is possible to remove some, or all the colouration of such diamonds under high temperature and high pressure (HTHP) to create the desirable white diamonds.

A Brilliant Blue Glow

Some diamond authorities have noticed a dancing blue effect from type 2a diamonds. The effect is not fluorescence and seems to be dependent upon the lighting under which the stone is viewed. Bright, unpolluted, daylight being the most likely situation to see the blue glow. It is estimated that only around 30% of type 2a diamonds exhibit the effect and the cause is, at this time unknown.

How To Identify a Type 2a Diamond?

Unlike the 4Cs of diamonds, the diamond type is not usually shown on a diamond grading report. Because the different types of diamond differ from one another at the atomic level identification cannot be carried by visual inspection; identification requires sophisticated equipment.

To test for the type of diamond an infrared spectrometer is used to check which wavelengths of light are absorbed. The absorption pattern gives the analyst information that enables a determination to be made.

Type 1 diamonds absorb brown and yellow wavelengths, type 2b diamonds absorb blue. Due to the lack of impurities, type 2a diamonds allow all visible wavelengths to pass.

It is quite possible that you already have a type 2a diamond without knowing it. The GIA and other diamond grading labs do not, as standard, report on diamond type due to the expense of doing so.

The GIA does offer a supplemental type testing service at additional cost. The lack of grading reports means that any older, very white, diamonds could be a type 2a but were mined before we knew about the different types. More recently, because most gems are not tested using the sophisticated spectrometer equipment required, the grading certificate carries no information about the type of diamond.

Why Would You Buy A Type 2a Diamond?

The rarity of type 2a diamonds means that they can command a price premium of 5-15% over other diamonds. For collectors and investors in diamonds, the price premium makes these diamonds a worthwhile addition to their collection.

At auction, these 'whiter than white' diamonds can sell for very high prices due to their fabulous appearance.

If you are not a collector, type 2a diamonds are an exquisite, if costly, choice for those seeking the very best in a diamond. They are usually almost flawless and have the best brilliance making stunning jewellery.

Such diamonds are a beautiful symbol of purity and love when given as a gift in a piece such as an engagement ring. For the lover of the very best things in life, an FL or IF type 2a diamond with a perfect cut is the epitome of perfection.