The Four Diamond Types – Explained

Everyone has a basic understanding of the diamond’s colour, clarity, cut & carat weight…the  four C’s of diamonds.   However, diamonds are also broken into four types – type Ia, type Ib, type IIa or type IIb.   These types relate to the amount of chemical impurities found within the stone.   Here is a brief description of the differences:

Type I Diamonds

The most common of the world’s diamonds, this is broken up by type Ia and type Ib.    Decidedly unsexy, these stones contain nitrogen impurities that tend to dull their appearance.

Type Ia Diamonds represent 98 per cent of the diamonds recovered in the world.   The nitrogens within the diamond are formed together within the structure of the atoms of stone called the carbon lattice.   This inner structure allows the stone to absorb blue light and appears to give it a yellow or brown colouring.

Type Ib Diamonds constitute less than 0.1 per cent of the diamonds in the world.   With these stones, the nitrogen impurities allow the absorption of both blue and green light.   Like the type Ia diamonds, they appear to look yellow or brown but that colouring is more intense.

Type II Diamonds

These diamonds have no nitrogen impurities.   Geologically speaking, they were simply under pressure for a longer period of time than type I diamonds.

Type IIa Diamonds represent between 1 and 2 per cent of the diamonds found on the planet.   This is the ideal type for high quality diamonds.   They are made up of pure carbon usually making them colourless diamonds.   However, if the carbon lattice is not perfect, it will allow the absorption of some light.   This absorption is what helps create diamonds that appear pink, yellow, purple, blue or brown.   Famous Type IIa diamonds include the Hope Diamond, the Cullinar diamond and the Pink Star.

Type IIb Diamonds represent less than 0.1 per cent of all diamonds and like their Type IIa cousins, they contain no nitrogen.   However, what separates these rare stones is the presence of the boron.   This element gives these types of diamonds a blue or red colour.