Last updated on October 9, 2020
Diamond inclusions are clarity characteristics that develop when diamonds are formed deep in the earth. The size, quantity, placement and colour of these inclusions determine a diamond’s clarity grade and affect its price. Here we have brought together different types of diamond inclusions to give you an idea of what they mean and how they look alike.
What Are Diamond Inclusions?
Diamond inclusions are natural birthmarks that develop when a diamond is formed in the earth’s mantle layer at depth of 80-120 miles.
Depending on the size, nature and quantity, diamond inclusions may or may not be visible to the naked eye, but they are always visible to a skilled grader under 10x magnification.
Since diamonds form under extreme heat conditions (up to 2,200 degrees Fahrenheit) and their growth takes between one to three billion years, only rare diamonds emerge in a truly flawless condition. Most of them are imperfect and contain different types of inclusions which affect a diamond’s appearance, clarity grade and the price as a result.
Types of Diamond Inclusions
As the name suggests, this type of inclusions looks like hair at the girdle area that occurs during the improper diamond cutting process. A heavily bearded girdle looks grey and fuzzy as if it has been scratched. Such diamonds should be avoided as this effect detracts from a stone’s beauty.
A cavity inclusion is a small slightly deep curved area typically caused when a crystal near the diamond’s surface is removed during the cutting or polishing process. Such inclusions accumulate dirt and oil and become darker and more visible with time.
Of course, these cavities could be removed during the polishing process, but to completely remove a cavity inclusion from a diamond’s surface, a cutter needs to recut or repolish the diamond which would result in a weight loss. That is why cutters prefer to retain higher weight at the expense of a lower clarity grade.
Pinpoint and Cloud
Pinpoints are miniscule white or black mineral crystals embedded within a diamond, sometimes even diamond crystals within the diamond. They look like tiny dots and out of all diamond inclusions, pinpoints are considered to be the most benign.
Cloud is a term to define a cluster of pinpoints found very close to each other that are seen as some hazy form. It’s not a big issue when clouds are small and diffused, but when the clouds get big they can negatively affect a diamond’s appearance and make it look hazy.
A crystal is a diamond or other material in its natural raw form that is embedded within the stone. Crystals are often colourless or various shades of white, however, they can be any colour. On rare occasions, these crystals can be especially unique and beautiful when they form shapes such as a bumblebee, dolphin, heart etc.
Feather or Cleavage
A feather is a small fracture within a diamond’s internal structure. Depending on your viewing angle, a feather can be almost invisible or catch on light and look like a small white feather within a diamond. Rarely feathers may also have a grey and brownish colour and they are noticeable to the naked eye.
Massive feathers can cause durability issues, especially if they reach the surface or the girdle, which is why such diamonds should be avoided.
Internal grain lines are gentle, usually colourless lines caused by irregular growth patterns during the diamond’s formation. Depending on their severity, they can also appear as creases giving a diamond milky or hazy appearance.
The knot inclusion is a white or transparent crystal that reaches the polished diamond’s outermost surface area.
As the name suggests, a needle is a long needle-shaped inclusion that is usually transparent or white. If in clusters, they have a dramatic effect on a diamond’s clarity grade and appearance.
A twinning wisp is a string of small pinpoints, clouds or crystals produced by an irregularity in the crystal structure. Such irregularities occur when a diamond stops grow because of unfavourable conditions and restarts growth in a different direction.
Can Diamond Inclusions Appear After Purchase?
Diamond inclusions are permanent. They don’t appear or disappear suddenly and there is no way a new inclusion can occur within your stone.
If you notice there is a new black dot or a line, that should be dirt particles that accumulate on a diamond’s surface over time. Dirt blocks light and reduces the stone’s sparkle, making internal flaws more visible. That is why you should clean your diamond at least twice a month.
Diamonds can develop external flaws like cracks and chips, however, they are not considered inclusions and may be fixed by professionals.