Diamond crystals can be light or dark and absolute or relative in appearance. In other words, a crystal may be light or dark in color, or it may appear that way due to lighting conditions.
First, the lighting used to illuminate diamonds for clarity photography often makes the clarity characteristics look dark. That is because the light source is positioned behind the diamond and thus the inclusions are being backlit.
Second, most diamond clarity photographs are taken using a light source that is positioned directly below the diamond. While the camera is located above the diamond.
Since the diamond crystal is located above the light source, it interrupts the light as it passes through the diamond. In this situation, it’s common for inclusions to seem dark even when they are light or translucent in color.
This is why people look dark in sunset photographs on Instagram when the sun is setting behind them. As a matter of fact, the subject will appear dark in that photograph unless a flash is used to offset the effect of the light source being behind the person being photographed.
The Effect of Lighting on Inclusion Appearance:
Sometimes the use of an additional light source positioned to the side or top of the diamond and directed towards the same diamond crystal will result in the inclusion appearing more translucent or lighter in color.
In contrast, the same inclusion might look darker ifthe solitary light source is positioned beneath the diamond. Alternatively, the diamond crystal could be dark in color and no amount of lighting will change the appearance.
Take this 1.09 carat, H-color, SI-1 clarity, James Allen True Hearts diamond for example. The dark crystal that is visible in the middle of the table facet looks to be pretty dark. At the same time, the inclusion is larger and size and easy to see in this clarity photograph.
Are Lighter Diamond Crystals Harder to See?
People often assume that diamond crystals that are lighter in color are more difficult to see within a diamond than inclusions that are darker in color. However, this is not necessarily true. The size, structure, and location of the diamond crystal will have a direct effect upon the visibility of the inclusion, the color of the diamond crystal is just another characteristic to be considered.
The easiest way to picture this in your mind is to simply consider whether a dark cloud up in the sky is any easier to see than a white cloud. With that in mind, it all depends on the conditions at that particular moment on that particular day because every cloud is different and the lighting conditions will have a definite effect upon your ability to see either cloud, light or dark.
When we look at clouds up in the sky, one of the factors which dictate our ability to see the clouds is contrast. As a matter of fact, this same principle is applicable when trying to locate inclusions within a diamond. In addition to the position of the light source having an effect upon the color of diamond crystals, the facet structure of the diamond, as well as the size, shape, and location of the inclusions within the larger diamond, will have an effect upon the visibility of the diamond crystals.
Every Diamond Crystal is Unique:
Because each diamond crystal is unique and no two diamond crystals are absolutely identical, each diamond crystal must be evaluated and considered on an individual basis and from a variety of vantage points in order to determine the visibility of the diamond crystal within the diamond being considered.
As a matter of fact, diamond crystal inclusions come in a variety of shapes and sizes. Some are extremely small, the size of a pinpoint and thus are deemed “pinpoints” on the key to symbols on the plotting diagram located on the diamond grading report. Other diamond crystals are long and thin and thus referred to as a “needle” and others are larger and simply called “crystals” while small clusters of pinpoint size diamond crystals are referred to as clouds.
Diamond grading reports do not provide insight into the relative translucency or “color” of the diamond crystal because of the effect which the light source used to locate the inclusions within a diamond can have in terms of whether the diamond crystal appears to be light or dark.
Does the Color of Inclusions Affect Durability?
I was recently asked whether the color of a diamond crystal has any effect upon the durability of a diamond. As a matter of fact, the color of an inclusion has no effect upon the durability of the diamond, nor the structural effect of the inclusion upon the diamond crystal.
It is simply an identifying clarity characteristic. The potential for any inclusion to have an effect upon the durability of a diamond is the result of the overall size and nature of the inclusion in terms of the relative position within the diamond, whether it is located near the surface or edge of the diamond and/or effects the integrity of the actual crystal structure of the diamond.
For instance, a “twinning wisp” which is the result of an actual twisting of the crystal structure of the diamond has the potential to present a durability risk because it has a direct effect upon the crystal structure and the cleavage planes within the diamond. A “knot” which is similar to a knot located within a piece of wood has the potential to present a durability risk to a diamond.
Consequently, that's because a knot can “pop” out of the stone under the right circumstances. Under those circumstances, it will leave a cavity. That is a hole within the crystal structure poses a similar durability risk to a cavity within a tooth or any other substance.
Of course, none of these inclusion types are necessarily a durability risk on their own. They require additional factors such as pressure, dramatic changes in temperature and being struck to pose a viable durability risk to the longevity of a diamond. As that may be, I prefer to take the safe approach and avoid them entirely.