Let’s start with some of the basics: where do diamonds come from?
Diamonds are formed in the earth’s crust, between 1 and 3.5 billion years ago, at about 150-200km below the surface. The temperature is 900-1300°C and the pressure is extremely high. There is also magma present, which may expand, forcing a volcanic eruption which results in the diamond containing rocks to be thrown towards and above the surface of the earth.
When diamonds are found in rock, they are called a ‘rough’ crystal. It is where this volcanic activity once happened, millions of years before, that we find diamond mines. Additionally, sometimes you can find diamonds in locations where natural geography or weather has carried them away from the original volcanic site, such as along river beds or sea beds.
But what is a diamond?
Diamonds are made of carbon, bonded together in an extremely tightly packed and strong lattice. This is what makes diamonds so strong. In fact, they score the highest, a 10, on the MOHS scale, which is essentially a scale of hardness, and consequently many diamonds that are not good enough to be used in jewellery, are used within industrial and manufacturing processes (eg. drill bits!). There are, however, different types of diamonds that are formed from either the presence of impurities within this lattice, for example as nitrogen or boron or indeed the lack of impurities. We will keep things simple rather than get into the deep chemical structure of diamonds:
● 95% of all diamonds are a Type 1A - known as the ‘cape series’ - which fall along a spectrum of colourless to yellow tinted. This is due to nitrogen impurities present within the carbon lattice structure.
● A Type 1B diamond also has nitrogen impurities, but they are more evenly spread out throughout the chemical structure of the diamond, and the result is a much more intense yellow or brown appearance.
● You may have heard of a Type IIA diamond, which has almost no impurities, resulting in an incredibly clear, pure, ‘water-like’ appearance. These are also known as Golconda diamonds, after a mine in India known for its prevalence of this kind of diamond. You can also get some coloured diamonds within this category, which form as a result of a shift in the lattice structure as a result of the explosive volcanic eruptions. This is a process called ‘plastic deformation’ and forms pink, brown, red and orange colour diamonds.
● A type IIB diamond is a blue colour due to the presence of boron as an impurity; an example of which is the infamous Hope diamond. These diamonds are unique in that they conduct electricity as fluoresce a bright red under UV light.
Whilst this may not be a technically exhaustive description of diamond types, we think that it helps to understand how diamonds differ. Learning more about how diamonds are naturally formed only adds to their sense of mystery, intrigue and amazement - something so beautiful has been formed in such violent conditions, over such a vast expanse of time. And now, you may or may not be enjoying wearing one!
On a modern round brilliant cut, the culet will be a sharp point, but on older stones it will be a flat facet which is then visible as a little dot through the table at the top of the stone. The proportions of a diamond cut are very important, as it is all about how the light enters the stone, travels within it, and then is reflected back out through the table and into the eye of the viewer. If the proportions are not quite right, this doesn’t happen.
This can cause loss of light, resulting in visually poor performing diamonds. For example, if a diamond is too shallow, reflections of the girdle may be visible, creating a ‘fish eye’ effect.
Or, if a diamond is too deep, this can cause a ‘nail head’ effect, resulting in the diamond looking very dark in the centre.
Left: Fisheye Effect Middle: Ideal Right: Nail Head Effect
Diamonds truly are a magnificent gemstone that human civilisations have marvelled at for centuries. Whilst there is an increase in laboratory grown diamonds to be found within the jewellery market today, nothing can surpass the incredible journey made by naturally formed
diamonds that have come such a long way from the earth’s crust, to a mine, to then be cut and shaped to perfection and set within a special item of jewellery. Call us sentimental, but we just don’t think that the two compare!