A diamond reacts to incident light in three different ways. It allows some of the light to pass through; it reflects another part and refracts yet another part of the incident light. This scattering and refraction of light makes the diamond sparkle.

If the path or wavelength of the incident light is obstructed or deflected, the light show will not occur. Depending on the size and type of obstruction, this can give the diamond a dull and lifeless appearance.

Such impediments are caused by imperfections in the Opal diamond, which can be either internal or external or both. External flaws that appear on the diamond’s surface are known as blemishes, while internal flaws that appear within the diamond’s crystalline surface are known as inclusions.

Inclusions are naturally acquired by diamonds during their formative years deep in the womb of Mother Earth and resemble birthmarks. These defects are caused by irregular crystallization of diamond during its formation process.

Blemishes can be man-made during quarrying, cutting and polishing, or they can be acquired naturally.

One must clearly understand that deep inside the earth, diamonds are formed in the harshest environments under unimaginable temperature and pressure conditions. These conditions are far from those of a sterile laboratory.

It is therefore normal for diamonds to have inclusions. Inclusions are usually present in diamonds rather than exceptionally.

Still, inclusions need not be viewed with distaste when they are small and only marginally affect a diamond’s brilliance and clarity. In fact, the inclusions present in individual diamonds are as unique as the human fingerprint and are recorded in detail in the diamond’s gradation report.

Most inclusions do not detract from the beauty of a diamond and are considered distinguishing features. They allow you to properly identify your own diamond in the event it is lost, stolen or confused with other diamonds when given for cleaning or appraisal.

However, if the inclusions are too dense or widespread, they can affect the diamond’s properties in a variety of ways:

Diamond brilliance:

An inclusion affects the diamond’s ability to scatter and transmit light because it impedes the light passing through the diamond. Consequently, it reduces the brilliance of the diamond.

Durability:

Inclusions can significantly reduce diamond breaking strength.

Beauty:

Larger inclusions or colored inclusions detract from the beauty of the diamond.

Price:

The diamond’s value decreases as the size and number of inclusions increases.

Some examples of internal flaws or inclusions found in diamonds are as follows:

Plumage:

“Feather” is a general term for cracks that might be present in a diamond. They are hairline cracks in the stone that (as the name suggests) resemble feathers. Small feathers do not typically threaten the diamond’s structure unless they rise to the surface at the top of the stone, where they are particularly vulnerable to accidental strikes.

Depending on the direction in which you look, a feather can appear glossy and white, shiny, or transparent. Some feathers catch the incoming light and flash from transparent to bright as the stone is moved back and forth.

Compared to other inclusions, feathers pose a greater threat to the diamond’s durability as a hard blow can enlarge them at any time. Ultrasonic cleaning can further pry and expand the springs.

Contained crystals or minerals:

Diamonds can be infused with tiny crystals and minerals due to the extreme conditions they endure over the years of their formation. Very often these crystals are smaller diamond particles within a larger diamond. These foreign particles obstruct the play of the incident light and thus affect the clarity, grade and value of the diamond.

But there are times when the naturally implanted crystal can have a positive effect and add character to a diamond. For example, a diamond with a small garnet embedded in it would be a great personal choice for someone whose birthstone is a garnet.

Node:

Sometimes, during cutting and polishing, a trapped diamond crystal that sits near the diamond’s surface will reach the surface and open up to the surface, known as a nodule. It can cause a lot of trouble for the diamond cutter while shaping the diamond.

The node is visible like a bump on a facet. The boundary between the host diamond and the nodule can be viewed at high magnification and with appropriate lighting. You can also see the telltale drag lines next to the knot where tiny diamond debris was accidentally dragged across the surface by the polishing wheel.

Because the knot itself is a completely different diamond crystal, its growth pattern differs from that of the host diamond. Most of the time it is not possible for the diamond cutter to polish away the knot.

Knots can greatly reduce the clarity and thus the value of a diamond.

Cavities:

Voids are exactly what their name suggests. They are holes on the surface of the diamond. Voids can be caused by two reasons.

If a crystal that reaches the surface is pushed out during polishing or simply falls out, it leaves a gaping hole called a cavity. Also, when part of a feather breaks off near the diamond’s surface, leaving a deep, fissure-like opening, this is called a cavity. The telltale drag lines next to the cavity, where tiny diamond debris was accidentally dragged across the surface by the polishing wheel, distinguish a cavity from a chip.

Voids can appear anywhere on a diamond, including the crown, pavilion, or girdle. It can affect clarity, just like an inclusion in a diamond. However, a cavity has a more negative effect on the value of the stone, as the cavity can darken from accumulated dirt from everyday use.

Twinning Wisps or Intergrowth:

The term twinning wisps or intergrowth does not refer to a single inclusion but to a group of inclusions that have intertwined in a twin plane. This motley group consists of a mix of inclusions such as diamond crystals, feathers, fractures, crystals and pinpoint sized clouds.

These are formed during the stone’s formative years as the diamond crystal forms and grows. Typically, they are ribbon-like bands located in the center of the diamond that look like white streaks within the diamond, similar to stretch marks on a pregnant woman’s abdominal skin.

Twinned strands are more common in fancy diamonds such as heart shapes, pear shapes and triangles, which are usually made from twinned crystals. On the other hand, twin tufts can also be found in other diamond shapes based on the quality of the rough diamond used to shape the stone.

Cleavage:

Cleavage is a straight crack in a diamond (without feathers) in its cleavage plane. The cleavage plane is a weak crystal direction along one or more of diamond’s four octahedral planes.

Cleavage can make the diamond more brittle as it has the potential to break the stone in two. However, the tiny, imperceptible cracks do not directly affect the diamond’s composition, and tiny cracks that are invisible in a tabletop (face-up) position do not seriously affect the diamond’s clarity ratings.

Beard or beard belt or belt fringes:

As the name suggests, beard belt or belt fringes are beard-like strands of hair that appear around the diamond’s belt.

This type of inclusion consists of tiny feathers extending into the stone from the girdle surface and is the result of the haste in the hatching process when cutting the diamond to its original shape.

A thin bearded belt has very few and very fine feathers mottled around the edge of the diamond and may not degrade the diamond quality.

A densely bearded girdle has a multitude of feathers that together form a fuzzy gray border around the stone. It should be removed or refined by re-cutting the diamond.

Chip:

A chip is a shallow opening found on the surface of the diamond caused by chipping or gouging a small piece of the diamond. The opening typically has a rounded outline and occurs at the edges of the girdle, culet, or facet. (It should not be confused with the term “diamond chip” which refers to very small diamonds).

Because the chip is the result of damage occurring after cutting and polishing, it is not flanked by trailing drag lines

Usually, most chips are too small to be significant and can be removed from the diamond surface by recutting or polishing the gem with negligible carat weight loss. On the other hand, larger chips may require re-cutting the entire diamond, resulting in significant diamond weight loss.

Dark point:

This is a thin, flat inclusion or small crystal inclusion that reflects light like a mirror. The inclusion could also appear as a metallic silvery reflector.

Points:

Are tiny crystals that appear like whitish dots (occasionally they may be dark in color) in a diamond and are difficult to see. They look like tiny dots at 10x magnification.

Sometimes the tiny dots can clump together, giving this area called a cloud a blurry look. A cloud can negatively affect the clarity of a diamond.

Clouds:

As mentioned above, clusters of tiny dots that cause blurry, cloud-like areas in the diamond are called “clouds”. They create an ugly stain on the diamond, lowering its clarity rating and value.

Individually, the pinpoints may be too small to distinguish at 10x magnification, but crowded together they appear as fine white or gray specks. Some clouds look like a light haze while others are dense and almost opaque.

Laser Lines

Unlike most other diamond inclusions, laser lines are artificial rather than natural. When a laser beam is used to remove dark inclusions in a diamond, the rays leave behind vapor-like trails called laser lines.

The markings look like filaments extending inward from the diamond’s table and terminating at the point where the inclusion was removed.

Laser drill hole:

Laser treatment is often used today to make the inclusions in a diamond less visible and also to improve the aesthetics of the stone.

The laser borehole is a tiny tunnel created by a laser beam. The tunnel extends from the surface to a darkly trapped crystal (or to the point where such a crystal has been removed). After drilling, sulfuric acid is introduced into the drill hole by dipping the diamond in the acid to dissolve or bleach the inclusion and make it less visible.

The fine bores are easily recognizable under microscopic examination. They are whitish and straight, but can also change direction slightly. They are often described as “wrinkled”. In the reflected light, the holes reaching the surface can be seen as dark circles opening through the facets of the diamond.

The Gemological Institute of America ranks laser drilled diamonds because the holes are permanent features and the drilling aspect is noted in the comments section.

Growth or grain lines:

It is well known that the transformation of carbon into diamond occurs under conditions that are far from ideal or sterile. Grain lines are created by irregular crystallization that takes place when a diamond forms.

These can only be observed while slowly rotating the diamond to be examined. They appear and disappear instantly, and usually appear as groups.

Colorless grain lines do not usually affect the diamond’s clarity unless they are present in large masses and can be seen from the crown side of the diamond.

Internal grain

Internal graining is also caused by uneven crystal growth and can appear like lines, angles, or curves. It can be colored, whitish or reflective. The internal grain can give some or all of the stone a hazy texture.

Fracture Filled

Surface-reaching springs and laser drill holes are sometimes filled with substances such as molten glass in a treatment called fracture filling. The filler makes the mistake less obvious.

It can be difficult to spot, but treatment leaves a telltale sign called the flash effect. It refers to the bright flashes of color seen when a fracture-filled diamond is rotated. The colors of these flashes range from electric blue or violet to orange or yellow, depending on the lighting conditions. Flashes are best seen when the visual field is approximately parallel to the plane of the filled fracture.

The Gemological Institute of America does not grade fracture-filled diamonds because the treatment is not permanent.

Bruise

A bruise is a tiny area of impact (Edelstein small chipping or concussion on the stone) surrounded by small root-like feathers visible at 10x magnification. When viewed through an opposite facet, a bruise appears fluffy in texture as it radiates into the diamond.

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