Category: Diamond 101

A knot is an inclusion crystal that stretches all the way to a diamond’s surface. To put it simply, it is a tiny mineral crystal inside the diamond. During cutting and polishing, the stone is ground down until this inner crystal gets exposed. It starts as a regular inclusion, most often another diamond crystal or other mineral crystals. Since it breaks through the diamond surface, it counts as both an internal feature and an external blemish. That is why we need to pay extra attention to knots when picking diamonds. A knot is one of the most noteworthy clarity characteristics. It can bring real troubles to a diamond’s durability and overall look.

Why do we need to watch out for diamond knots?

A knot will lower the diamond’s clarity grade. More importantly, it leads to two major problems.

Durability Risk

This is the biggest concern. A knot sticks out on the diamond surface, so it is much weaker than the surrounding stone.

It chips easily. When being set into jewelry, especially under pressure setting, or hit and bumped during daily wear, the raised knot will chip far more easily than the rest part of the diamond.

It also makes maintenance hard. Even during regular jewelry cleaning or repair works, wrong operation may damage this fragile spot.

Visibility & Appearance Issues

White knots usually are small white or transparent dots if they are made of diamond crystals. As they sit right on the surface, their reflection is different from the main diamond. Sometimes they stand out more than other inclusions of the same size deep inside the stone.

If the knot consists of other minerals like garnet or pyroxene, it will turn dark or black. Dark knots are highly visible and do far more harm to the diamond’s appearance.

How to identify a knot on a GIA report

On the GIA clarity plot diagram, knots are marked with red symbols. Red marks always stand for features that reach the stone’s surface.

A knot may be labeled as a small dot or circle on the diagram, with the short form “Knt” next to it.

Here is an important tip. You have to check both the plot diagram and the written description. The diagram show you the exact location, while words like “Crystal, Knot” tell you what the inclusion is.

Buying advice: What to do when a diamond has a knot?

Try to avoid it first

For most buyers, especially those shopping for engagement rings worn every day, it is wise to stay away from diamonds with knots. This can save you from potential damage and appearance issues in the future.

Evaluate the situation carefully

If a diamond catches your eye for its great color, carat weight and good price, you need to make a full assessment.

Check its size and position. How big and noticeable is this knot? Does it locate on the pavilion or the crown?

Knots on the pavilion have lower risk. They are usually protected by prongs and the ring shank. They are hard to hit and barely visible from the front view.

Knots on the crown or girdle carry very high risk. These areas get hit all the time in daily life. Knots near the girdle are extremely easy to break during stone setting.

Check the clarity grade. If a diamond is graded SI clarity and its main inclusion is a knot, you need to be extra careful. Such knots are likely to be seen by naked eyes and even felt by touch. If the diamond is VS grade or higher, the knot is usually tiny, so the risk is much smaller.

Always check the real stone in person

Look closely. Use a magnifying glass to check the knot’s size, position and how much it sticks out.

Touch the surface gently. Feel if the knot is raised above the diamond.

Choose reliable sellers. Buy from trusted merchants who provide 360-degree high-definition videos. Watch the videos carefully to study the knot’s condition. Honest sellers will always tell you about the hidden risks clearly.

Conclusion

Knots are not the most common clarity characteristics, but they are definitely ones we cannot ignore. They ruin the diamond’s look and also create hidden durability risks.

Unless you fully understand and accept all the risks, or the knot is extremely small and placed in a safe spot, you had better choose a diamond without any knot for long-term wearing. A diamond with other inner inclusions, such as small internal crystals, clouds or feathers, is much safer than a diamond with a surface knot.

The name Flying Saucer Diamond is really vivid. It describes a diamond with an extremely shallow pavilion. When you look at it from the side, the girdle looks extra wide, while the pavilion part is extremely thin. The whole stone looks just like a flying saucer or a flat button.

This kind of cut has only one bad purpose. Cutters keep as much carat weight as they can, and make the table look much larger than it really is. It tricks buyers into thinking they get a big diamond. In diamond cutting industry, this is a clear negative term and a serious cut defect. It is also know as a worse version of fish eye diamond, or the extreme form of fish eye effect.

A flying saucer cut go against the core idea of diamond cutting. The goal of proper cutting is to maximize a diamond’s brilliance and fire. This bad cut brings many serious problems.

First, the diamond loss all brilliance and fire. It looks totally dull. A diamond shines because light enters the stone. The light reflect fully between pavilion facets, and finally bounce back through the crown to our eyes.

For flying saucer diamonds, the pavilion is too shallow. Light cannot reflect inside. It leaks straight out from the bottom. The stone turns dim and lifeless. It looks just like a plain piece of glass, with no sparkle at all. This is its biggest and worst flaw.

Second, it has obvious girdle reflection, also called severe fish eye effect. When you look down from the table, you will see a big, pale grey ring. This is the reflection of the thick girdle. The ring is large and clear. It makes the center of the diamond look empty and ugly. The whole stone lose its beauty completely.

Third, the structure is weak and easy to damage. The pavilion is super thin, so the girdle area become fragile. It is easy to get chips or cracks during setting or daily wear. This type of diamond has very poor durability.

How to spot a flying saucer diamond from a GIA certificate?

Do not only trust the overall cut grade. Some flying saucer diamonds can even get Good or Fair grade. You have to check the Proportions chart on the certificate carefully.

Pavilion Depth percentage is the most important index. If the number is below 40.0%, the risk is very high. A typical flying saucer diamond may have pavilion depth of 37% or even lower.

Total Depth percentage will also be too low. Total depth shows the full height of a diamond. Normal round diamonds have total depth between 57% and 63%. Flying saucer diamonds usually have total depth under 56%.

The Crown Angle is abnormal too. Cutters often use a very small crown angle to match the ultra-shallow pavilion.

The Girdle is extremely wide. The certificate marks girdle thickness. Most of these diamonds are marked Thick to Extremely Thick. Cutters barely polish the girdle, just to save weight.

Here is another easy way to judge. If both Pavilion Depth and Total Depth are unusually low, it is almost certainly a flying saucer diamond.

How to avoid buying this kind of diamond?

Learn to read the proportions on GIA reports. This is your first line of defense. Stay away from diamonds with pavilion depth below 40.0% and too low total depth.

Never buy a diamond only by its certificate. No matter how good the data is, check the real stone or watch 360° high-def videos from trusted sellers. Turn the diamond around. If you see a big grey ring on the table and no sparkle, do not buy it at all.

Choose reliable sellers. Pick well-known jewelry stores or online platforms, such as Blue Nile, James Allen( now belongs to Blue nile) and Whiteflash. They will filter out poorly cut diamonds in advance. They will not sell these bad stones to customers.

The fish eye effect is a common optical issue in diamonds. When you look straight down from the table, you can see the reflected edges of the pavilion facets. It forms a pale grey or white ring, just like the eye of a fish. A diamond with fish eye effect looks dull and lifeless. There is a dark empty circle right in the center. It lose its normal brightness and fire completely.

This problem is caused by poor cutting, which leads to serious light leakage inside the stone. The diamond looks dim and unattractive, just like a dead fish’s eye. This also tell us an important truth. We cannot choose a diamond only by the GIA Excellent cut grade. A high grade on paper does not always mean the diamond perform well in real view.

When you buy a diamond, you must check both the certificate data and the actual appearance of the stone. In this way, you will not only get a nice report, but also a real brilliant and beautiful gem.

What causes the fish eye effect?

The main reasons come from improper cutting. It mostly happens when the total depth is too shallow, and the crown angle and pavilion angle do not match well. Here are the key causes in detail.

First of all, a shallow pavilion. If the pavilion angle is too small, or the pavilion depth percentage is too low, light cannot create total internal reflection inside the diamond.

Then light leakage occurs. Instead of reflecting back to your eyes through the table, light escape directly from the sides of the pavilion. This is the core of the problem.

Because of such light loss, you can clearly see the reflection of the diamond’s girdle when looking from the top. A white grey ring will appear around the center. That is exactly the fish eye we talk about.

Here is a simple example to help you understand. Imagine a swimming pool that is too shallow. Standing on the bank, you can easily see the tile lines along the pool bottom. You cannot feel the deep sense of water at all. It is the same logic with diamonds.

How to spot potential fish eye effect from a GIA certificate?

We cannot confirm the problem 100% only by papers. But you can check the proportions section on GIA reports to rule out high-risk diamonds.

Low pavilion depth percentage is the biggest warning sign. Generally speaking, if the pavilion depth is below 40.0%, the risk of fish eye effect is very high.

A too small crown angle will make the situation worse. When crown angle is less than 30.6°, matching with a shallow pavilion, the fish eye issue become much more obvious.

Besides, an overly large table also raise the risk. When table percentage is over 62%, there are fewer facets to spread light evenly inside the diamond.

You need to keep one thing in mind. Even if the diamond is graded Excellent in cut, it may still have slight fish eye effect. GIA cut grading covers a range of proportions. Diamonds at the lower limit of Excellent grade often have much worse optical performance than top-level stones in the same grade.

How to avoid buying diamonds with fish eye effect?

Never buy a diamond just based on its certificate. This is the most important rule. Certificate is just a basic reference. Real inspection or high-definition videos are the key.

Study the proportions on GIA certificates carefully. Try to pick diamonds within the safe range. These are the ideal proportion ranges recommended in the industry:

Pavilion Depth: 42.5% to 43.5%

Crown Angle: 34° to 35.5°

Table Percentage: 54% to 58%

Total Depth: 59.0% to 62.5%

These are standard ideal ranges. A little out of the range does not definitely cause problems. But the further it deviates, the higher the risk will be.

Always check the diamond in person, or ask the seller for real videos.

If you can see the stone face to face, place it on a white paper. Look down from the table. If you notice a vague white or grey ring in the center, it has the fish eye effect.

If you shop online, ask reliable sellers for 360° high-definition videos of the diamond. Watch the video slowly. Turn the stone and check the front view again and again for any sign of fish eye. Trustworthy merchants will not sell such defective diamonds secretly. They will take initiative to tell customers about all existing flaws.

Buying diamonds just based on certificates is a very risky move. You may end up with a stone that has perfect data on paper, but looks disappointing in real life. Certificates like GIA reports work like ID cards for diamonds. They prove the basic features and official grades, but they can never guarantee how beautiful a diamond looks. Buying a diamond only with a certificate is just like hiring an employee only by their resume. A resume, which is similar to a diamond certificate, shows education, work experience and skills, just like the 4C standards on a report. But you cannot tell their real work attitude, communication skills and team work spirit. These equal to a diamond’s actual look and sparkle. If you do not want to spend a lot of money and feel regret later, you must check both the certificate and the real diamond. Do not just pay for a nice report. Choose a diamond that is truly bright and stunning.

Here are the main problems you may face if you only trust the certificate. First, you will miss the most important part: real appearance and optical performance. The 4Cs including color, clarity, cut and carat weight are graded by lab experts under controlled environment. However, people wear diamonds to admire their beauty, not to lock the certificate in a safe. Many people fall into the trap of milky diamonds or coffee diamonds. Some diamonds have massive cloud inclusions inside. They look foggy and hazy, which we call milky diamonds. Some carry obvious brown tones, known as coffee diamonds. Even if their clarity grade is not low, such as SI1 or VS2, those clouds will badly hurt brightness and transparency. The diamond looks dull and lifeless. Sadly, this kind of visual problem are not noted on most certificates.

A top Excellent cut does not always mean great sparkle and fire. There is a big range within the Excellent grade. Two diamonds both marked Excellent cut can be totally different. One with cut proportions just meeting the standard, and another with perfect proportions. Their sparkle, fire and brightness can have huge gaps. You can never know these differences only from a piece of paper.

Poor symmetry and polish are also common issues. Bad symmetry makes the table tilt and girdle uneven. It blocks light reflection and ruins the overall beauty. These details are written on certificates, but ordinary people can not imagine how bad they look in real view.

Second, you cannot judge a diamond’s unique charm and beauty. Every diamond is just like a person, it has its own style.

The position and visibility of inclusions matter a lot. Take two VS1 diamonds for example. One has inclusions hidden at the pavilion, so you can not see them from the top table. The other has marks right in the center of the table, just like obvious dust. The plotting diagram on the certificate marks the position, but you need to see the stone in person or watch professional photos to tell how noticeable it is.

Diamond fluorescence also creates different visual effects. Certificates mark fluorescence levels: none, faint, medium, strong and very strong. Strong fluorescence may make diamonds look foggy under sunlight and reduce clarity. On the other side, faint to medium fluorescence can make slightly yellow diamonds such as color J and K look whiter. This is a visual feeling you have to see yourself, you cannot tell good or bad just from words.

Third, you may buy so-called “data diamonds”. Many online sellers and wholesalers sell this kind of stones. They have perfect certificate data, but plain and ugly appearance. They know many buyers trust GIA reports and 4C numbers too much. They buy these flawed diamonds at low cost, then sell them with the slogan of high cost performance. You think you get a good deal, but actually you get a dull diamond with no shine.

Now let’s talk about the right way to buy diamonds: combine certificate check and real product evaluation.

A certificate is necessary for reference and quality guarantee, but it is not everything. Follow these steps.

Set your budget and 4C range first. Use the 4C rules to narrow down your choices. Read the plotting diagram carefully. Stay away from diamonds with inclusions on the table center or large cloud inclusions. Also make your choice on fluorescence level.

The most important step is to view the real diamond or watch professional videos.

If you visit physical stores, check diamonds under professional lights and natural daylight. Compare fire, brightness and transparency between different stones. Ask the shop staff to put several options together for comparison.

If you shop online, pick reliable sellers. Choose stores that provide high-definition magnified videos, 360° views, ASET and Idealscope images. James Allen ( note in 2026, james allen has joined bluenile) and Blue Nile are trustable online jewelry stores. These materials clearly show a diamond’s optical performance, making up for the lack of in-person viewing. Videos are much more reliable than static pictures.

Last, work with reputable jewelers or diamond consultants. They have rich experience and can guide you to avoid common traps.