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What are diamond carbon spots?

A diamond is comprised of nearly pure carbon. So how is it that they can have dark carbon spots? These inclusions, also called flaws, might give you pause when considering a stone. What is a diamond carbon spot and should one prevent you from making a purchase?

As a creation of nature, a diamond will rarely be truly flawless. Even a stone graded as ‘flawless’ will have some imperfections. They will simply be very difficult to see with the naked eye. The art of diamond cutting aims to reduce the number of inclusions and flaws while maintaining the weight and natural beauty of the stone. However, a few small imperfections will always remain to remind you that this is indeed a natural stone and not one grown in a lab.


Dark blemish

One of the most common inclusions is a dark blemish called a carbon spot. Diamonds are but one form of carbon; there are many others and most of them are black. Graphite, charcoal and lampblack are all types of carbon as well and there really isn’t a defined line between the various forms.

Diamonds are frequently found in formations along with large areas of opaque black crystallisation. Some of the dark colouration may also be found within a diamond itself. Carbon spots appear in many forms. They can be a tiny pinpoint only visible through a microscope or large enough to see with the naked eye. They can appear as a cloudy haze or a sharply defined needle darting through the stone. They might be a clustre of spots or a vague shadow only seen in certain angles.


Theories of formation

No one is quite sure why or how carbon spots form in diamonds. The raw materials were ostensibly exposed to the same heat and pressure so why some of it forms a clear crystal and some an opaque black substance is a mystery. Some theorise that a carbon spot is the nucleus around which the crystallised diamond grew and that starting point was somehow excluded from crystallisation.

Another theory is that some critical factor or chemical was not evenly distributed within the raw materials. Whatever the cause of their existence, carbon spots are some of the most common inclusions in diamonds. This kind of inclusion, while common, isn’t very desirable, especially in white and light-coloured stones. Carbons spots visible to the naked eye can diminish clarity, which is one of the primary grading criteria for diamond quality along with cut, colour and carat weight. They interrupt the way light passes through the clear planes of the diamond and that may reduce the stone’s sparkle and beauty, which will reduce its value.


Signal of weakness

In addition to affecting the clarity of the stone, a carbon spot may also signal a weakness in the stone’s structure. Any inclusion is a naturally occurring weak point within a diamond. Flaws that are close to the diamond’s surface or extend through the surface are especially prone to cracking and cleaving. A sharp blow, a rapid change in temperature, or the continued pressure from the setting can turn a flaw into a fissure or worse.

A well-cut stone usually avoids the pitfalls of carbon spots, both in beauty and in durability. The cutting process that creates the beautiful stone you see in your setting is equal parts art and science, but it will never render a perfect product. A natural diamond is a wondrous thing, flaws and all, just like the person who wears it.

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