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Types of Diamond Inclusions and their Characteristics

Types of Diamond Inclusions and their Characteristics

Types of Diamond Inclusions and their Characteristics

Posted by Sharif Khan on 3rd Dec 2019

Types of Diamond Inclusions and their Characteristics

Flaws are to diamonds what stains are to clothes. And you know what they say about a stain: “its worse when you can’t see it.” Maybe you know all about the  4Cs of diamond quality. A stone’s description such as 1.5ct, J color, excellent cut, VSI1 round brilliant is readily recognizable to you. If this is the case, that’s impressive. It means you’re an informed buyer. However, imperfections (inclusions and blemishes) are a different ball game. That’s because you have to go beyond the  diamond certificate (and beyond the 4Cs) to understand them.

Several inclusions double up as flaws making the diamond vulnerable to damage. Others are unique stone identifiers and contribute to the diamond’s natural aesthetic appearance. You might have heard of diamond cloud and feathers, but do you have any idea what etch channels are? How about an indented natural? Better yet, what does “Manufacturing remnants not shown” or “Internal laser drilling present”mean when it appears on the diamond report? The answer to that and further insights into diamond irregularities make up the bulk of this text.

But first, a warning: never buy a diamond solely based on the contents of the stone’s certificate. In case you’re wondering, you didn’t read that wrong. If the certificate didn’t come from  AGS or GIA grading labs, always have a close-up examination of the stone. It’s the only surefire method to determine diamond eye-cleanliness.

The diamond industry has hundreds of vendors—both online and physical stores jewelers—which makes it super easy to find one. Working with an accredited dealer should be a no-brainer. But even when buying from a credible diamond seller, you can easily fall victim to diamond inclusions. The reason being that most diamond grading reports give a general  clarity grading, especially for stones below 1 ct.

James Allen

For instance, an inclusion characteristic could appear on the certificate as a crystal or feather. That’s a problem because you can’t tell the type and extent of the feather. You also aren’t able to know what kind of crystal is in the diamond. If it were a birthmark like pinpoints, it would make sense as these are mostly benign. Giving a clarity description such as crystal or feather leaves a lot of room for speculation and ambiguity. It’s simply not enough of a clarity reference for a diamond’s inclusions.

Technology is on your side. From that long list of diamond vendors, only work with those who incorporate diamond display technology. Or those who offer a rundown on diamond inclusions. Technology in the diamond industry means the use of advanced diamond cutting and polishing equipment. It also entails the employment of a special camera and imaging devices.

The cameras can capture magnified, enhanced images, and 360 0 interactive high definition videos of a stone. You can see all visible inclusions by observing 10x digital photos of the VS2 diamond and below. Your observation and in-person viewing of the stone is enough to make a call. If the stone is genuinely eye-clean, you can go ahead and negotiate a price for it.

Stay away from the dealers who demand part payment before disclosing the clarity details of a stone. Brokers are dangerous too. Most are in it for the money. They could sell you an eye-clean  princess cut with inclusions in the corners of the square shape. And before you know it, the stone is already chipping. GIA uses a plot or ‘map’ of the diamond’s geometrical shape, which features in all GIA certificates.

The clarity plot shows the exact location of the inclusion. To isolate the accurate position of a particular internal clarity characteristic or blemish, GIA uses red and green markings, respectively. A combination of red and green markings suggests the identification of inclusions that reach the surface of the stone. For example, cavities, etch channels, and laser drill holes. Black usually conveys the presence of extra facets. Check out the image below. For good measure, always check the comment section on a GIA or AGS certificate to get more details on clarity. And next time you go gem shopping, look out for the following diamond inclusions:

Bearding

When you see a diamond report that indicates the presence of beards in a diamond, please don’t take the literal meaning. Bearding is an inclusion that occurs when cutting the stone. Diamond cutting or bruting is a rigorous process that involves heating and grinding the rough diamond crystal. As a result, many tiny strands of hair appear around the diamond’s girdle, hence the term bearding. It’s worth noting that the hair-like inclusions only arise out of an improper bruting process. It’s a situation that can happen when the cutter is unskilled or lacks experience using cutting equipment. Bearding along the girdle of a diamond is relatively easy to spot on an enlarged diamond image.

A small presence of the hairs or beards doesn’t have much of an effect on the stone’s luster. Conversely, a heavily-bearded diamond girdle appears to have dark-greyish furs that affect the clarity grade of the stone. They could result in an SI2 grading when easily visible under 10x magnification. Other terms that gemologists use for this type of inclusion are girdle fencing, girdle fringes, and dig marks. You might come across the two phrases in diamond reports (depending on the grading agency) and different diamond industry publications.

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Crystals and Minerals

Diamonds form deep down the surface of the earth; well into the inner layers of the mantle at a depth of over 100 miles below sea level. The heat can be as high as 2000 degrees Fahrenheit and the pressure as much as 70,000 pounds per square inch. Such extreme conditions are almost guaranteed to leave imperfections in and on a diamond. Diamonds are the hardest mineral on the Mohs hardness scale (hardness of 10).

The conditions are also perfect for their crystallization. Other minerals and crystals form alongside diamonds. It’s common for other diamond crystals or foreign minerals to get trapped within a bigger diamond during its formation. Foreign minerals enclosed in a larger diamond include reddish crystals (garnets) or greenish ones that are mostly peridot. Other minuscule minerals or crystals embedded within a diamond stone may be iron oxide, silica, diopside, calcite, and spinel. It’s also possible to have smaller diamond crystals included within a stone. In such instances, gemologists call it a ‘baby diamond.’

The colored minerals aren’t a threat to the overall clarity of the stone, especially when in traces or scattered in the stone’s body. However, a concentration of minerals in one position could be easily recognizable under 10x. Or visible even to the naked eye. And that’s not a good look in terms of the clarity grade.

When dealing with baby diamonds, several interpretations can be made depending on the nature of the trapped diamond crystal. The baby diamond can resemble fancy shapes that add on to the beauty and uniqueness of the stone. Gemologists have, on rare occasions , spotted baby diamonds that have the shape of a dragon, a bumblebee, a dolphin, and even a heart shape. In such an encounter, whether the crystal is white, colorless, or colored, it's considered an extra gemstone. That’s two for the price of one! Baby diamonds and foreign crystals could also assume the shape and form of a needle, a pinpoint, or clouds. Each of these interesting shapes—in and of itself—is considered an inclusion.

Needle

When crystals within a diamond appear long and thin, they’re dubbed needles. They could be transparent and only visible in jeweler’s loupe amplified images. That means the stone probably has an SI1 clarity or higher. But if the needle crystal is colored, huge enough, or near the surface, it could be visible through the table, crown, or pavilion.

The needle or tiny rod-shaped crystals needn’t be huge or colored. Some are white, elongated, and clustered in one particular position, making them conspicuous to the untrained eye. You wouldn’t need a loupe or microscope to see them, either. Such a stone is in the clarity range of SI2-I3. It’s detrimental considering that most jewelers don’t even stock I2 and I3 stones.

Pinpoints and Clouds

A pinpoint is a type of crystal that could have a white or dark (black coloration). Pinpoints are one of the most common inclusions in almost all types of natural diamonds. They share that commonality with needles and feathers. Typically, a single pinpoint is so tiny that it’s said to be smaller than a speck of dust. Being tinier than dust particles means that a GIA-certified professional finds it difficult to identify a pinpoint even under 10x.

It’s only possible to locate the smallest of pinpoints under higher magnification, say 30x or 40x. Such a case warrants a "Pinpoints not shown" or "Clouds not shown" comment on the diamond certificate. It means that pinpoints are present, but only visible under a magnification beyond the industry standard (10x). Pinpoints on the clarity plot of your diamond’s certificate should be the least of your clarity concerns. What should make you a bit uneasy is the presence of a cluster of pinpoints or larger dark-colored pinpoints.

A significant concentration of white pinpoints creates a fuzzy dot in that area of the stone. The cloudy appearance hinders the traveling of light in the stone. A cloud in the crown of the stone stops light from piercing through the girdle and into the pavilion. Consequently, reflection and brilliance are affected. A grouping of closely-positioned pinpoints is called a cloud: an inclusion in its own right.

Dark pinpoints, on the other hand, indicate the presence of carbon or graphite crystals in the stone. Dark spots are harmless when unnoticeable to the naked eye. Darker and stark black spots, dead center in the middle of a diamond’s table are the worst. They’re visible to the unaided eye, especially in a large table, in step-cut stones such as  emerald and Asscher.

It’s better to have a dark-toned spot far off to the side of the stone away from the girdle and the surface. An excellent cut in the  round and princess cuts can do a great job of hiding black spots. The lightly dark spots in the pavilion and the edge of the diamond in contact with a metal setting are concealable with a prong setting.

Feathers

Feathers get their name from the resemblance to a bird’s feathers. Feather is an inclusive term that the GIA and AGS use for all cracks (fissures), fractures, and breaks within a diamond. They’re a relatively common imperfection. Though not known to be surface-reaching, they can be both appealing and provocative to the structural integrity of the stone.

When small, and particularly in SI1 diamonds or above, they’re never visible unless under magnification. The feathery look, location in a non-threatening position, and a colorless appearance make them docile inclusions. However, depending on the observation angle, the crack or fracture could reflect light and have an unsightly opaque aspect.

An extensive fracture, close to the surface or stone’s girdle should be a red flag. Some feathers are significant and could be far-reaching. That means a feather may start at a certain point in the crown and cut through the girdle to advance well into the lower half of the stone. Such a feather has since shed off its aesthetic appeal and places the stone in the lower rungs of the clarity scale. It qualifies as dangerous. Such feathers are visible to the human eye in I1 tones. They’re evident in both face-up and face-down stone orientations. The GIA clarity plot is usually keen to account for such an internal flaw.

When the feather breaks through the girdle, the durability of the stone is questionable. It’s likely to break with time. The risk of breakage is even higher when the feather exhibits areas of stress or happens to border included crystals. The tension could cause the crack to open up more forming a cleavage plane.

That’s a recipe for disaster, especially when the cleavage plane happens to be a straight line. Or parallel to one of the crystallographic planes of the stone. Breakage is inevitable upon an accidental blow to the stone. And if the feather is on the girdle, pressure from a tension setting could crumble the diamond. An extreme feather is an inclusion to avoid at all costs.

Bruises, Chips, Cavities

The GIA considers these internal irregularities different, though they share a lot of similarities. They almost look indistinguishable to non-professional graders and happen in a very closely related manner. A Cavity is the hollow space left behind after an included mineral is removed (accidentally or intentionally) during the polishing process. The included crystal must be close to the surface of the stone for it to be disturbed by a polishing wheel. A knot is a gemological term for such crystals. Similar to knots in wood, these white or transparent crystals partly sit in the body of the stone.

In some rare cases, the knot causes a facet directly above it to appear as though it's slightly protruding. The facet may be raised a bit in comparison to the surrounding facets. When removed, the resulting dent is an inclusion—a cavity. A chip is also an opening, though shallow than a cavity that appears on the stones surface following a sharp blow that causes damage to the stone. The presence of a different inclusion could precede it.

A perfect example is the presence of feathers near the edges of the stone. Or in the girdle, the facet intersections, or even on the culet. In the same vein, bruises are also synonymous with facet junctions. Bruises mainly occur on the crown. They could emerge when the diamond catches onto rough materials or from a forceful impact with a hard surface. At times feathers could arise out of the sharp blow that created the bruise. Take care of your diamond to protect it from this inclusion that could lead to a snow-ball of other clarity issues.

Twinning Wisps or Intergrowths

You already know the extreme conditions under which diamonds form. What you might know is that this formation process takes hundreds and possibly millions of years. The process could also be interrupted by a change in underground temperatures or pressure levels.

If this were to occur, a diamond develops irregularly, where the crystallization is uneven. At this point, diamond wisps and graining develop. The unevenness can cause twinning wisps, which fundamentally distorted crystallographic planes. It’s a growth defect in the stone’s crystal structure made of a series of overlapping pinpoints, clouds, included crystals and feathers.

Scientists call such stones macle diamonds. They often have fancy cuts (modified brilliant, step, mixed, rose, and mogul cuts) to navigate the wisps and inter growth. The abnormal formation could also result in the creation of a graining effect (both internal and surface graining).

Graining causes reflective, whitish, or colored lines deep within the body of the stone (internal graining) or closer to the surface (surface graining). Graining is only visible under 10x and has little to no effect on a diamond’s clarity. Heck, if it’s the only flaw ‘concern,’ that stone can easily pass as an internally flawless diamond.

Etch Channels and Laser Drill Holes

The human mind is always trying to innovate, and in the processes, pitting natural phenomena against technology. In the diamond industry, diamond clarity enhancement technology has been a hot topic full of controversy. Sections of diamond dealers are for it, while the rest have their doubts about it.

Gemologists have two views on etch channels: the natural and the human-made type. Remember, the diamond is born in the mantel, but has to somehow move to the crust (where it’s mined). During that movement, the heat and abrasion against other rocks facilitate scrapping of the stone’s surface. The cuts take the form of slightly hollow tunnels or parallel, or spiraling lines—scars or natural etch channels.

With the increased use of laser cutting tools, some marks (manufacturing remnants) could also remain on the surface of a diamond. In some scenarios, these mechanical marks show up as white or milky lines under 10x. For this reason, some graders recognize them as human-made etch channels. However, due to the preciseness of laser beams, you can only see the lines if you have bionic eyes (pun intended). That’s why GIA may leave a comment such as “Manufacturing remnants not shown” on the certificate.

Along the same line, clarity enhancement may entail the use of laser beams to drill holes that sink to the location of a dark crystal. A bleaching agent such as sulphuric acid is then used to bleach the crystal for a tonal color balance. The drill hole left is considered an inclusion. AT times, clarity enhancing technicians fill up the hole with halogen-based glasses. The colorless substance, for instance, lead-bismuth oxychloride glass, maintains that transparent look and feel.

Whether covered or not, the drill holes are so tiny and invisible. You can never see them without 10x, even if you have the strongest eyesight. And that explains certificate comments such as “Internal laser drilling present.” The GIA doesn’t grade clarity enhanced stones. Gemologists and jewelers are required to disclose clarity enhancement as a buyer-protection measure.

The most important lesson? Some inclusions are tolerable, but you should avoid the flaws. Lone standing pinpoints and indented naturals (part of the rough diamond below the stone's surface) aren’t a symptom of I clarity. Stick to GIA or AGS full diamond reports to avoid getting unwanted surprises on the clarity of your stone. Some jewelers disguise I1 diamonds with an SI3 clarity grade. GIA has no SI3 degree on its clarity scale. Steer clear of this marketing gimmick.

According to Blue Nile, online jeweler, SI1 and SI2 diamonds are the best clarity value for diamonds. But note that SI1 inclusions are sometimes visible to a keen observer without the need for image enhancement. SI2 inclusions easily show through the table and pavilion under 10x. So, take your pick with that information in mind.

Extreme inclusions affect the beauty, brilliance, and life of your diamond. To avoid them, go for VS clarity. VS1 clarity is better off than VS2. Instead of spending more money on a VVS2 stone, join 43 percent of diamond buyers and settle for a VS1 stone. It’s almost always guaranteed to be eye-clean, and gives you the biggest bang for your buck!