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How to tell good diamonds from bad?

The 4 C’s are probably already known to you as its common knowledge that they are the 4 core characteristics of diamonds: Color, Clarity, Cut and Carat Weight. One of the clients we mentioned before, had a bit of an issue with their diamond missing a bit of the down low on cut.


We’ll talk more about the most important C: the Cut.

It isn’t that easy to classify the Cut like the other 3 C’s. Color, Clarity grade and Carat Weight are easily measurable with the proper tools, and they are mostly visible. But the Cut is very difficult to see unless you are an expert. Many times there are disagreements between two experts about the value of a diamond, but it’s always obvious when there is a badly cut diamond. But first we’ll go over some basic info about how to tell good diamonds from bad diamonds.


The Difference Between Shape and Cut

The cut is the actual geometric proportion of the diamond facets, while the Shape is the general or basic outline of a diamond. The shape can be round, square, oval, cushion, or triangular, whereas the cut is the proportion of the facets and how many blemishes there are on each facet. For instance a certain shape like the popular round shape can come in many different cut qualities, from Excellent to Very Good, Good, Fair and Poor. The Cut gives the quality of the reflective light and causes the diamond to sparkle brilliantly. Many times you’ll hear a shape name with the word “cut”; this refers to the shape – not to the cut grade and you should notice that difference.


The Common Naming Convention Of The Diamond Parts

  • Table is the flat top of the diamond.
  • GirCulet is the point at the bottom of the diamond.
  • Pavilion is the portion between the girdle and the culet of a diamond.
  • The number of facets depends on the quality of the cut and the shape.
  • The best cut has each facet completely smooth and polished.
  • What’s Important to Understand About the Dimensions of a Diamond


All the measurements of the diamonds, i.e. diameter, width and height, are measured in millimeters and are referred to as the diamond’s dimensions. The ratio between the different parts mentioned above are called the proportions. A really good cut diamond with good proportions will be much more sparkly and shiny than a badly cut one with bad proportions, even if the rest of the C’s are identical.


Is There an Ideal Cut and Is It a Must?

There are well-defined proportions in the industry that maximize the shine and sparkle of diamonds; the experts call them “ideal” cut diamonds. Then the question to ask is why are not all diamonds ideally cut? The answer is sometimes the raw material doesn’t allow for the ideal cut. Since diamonds are found in nature as compressed carbon, sometimes there are carbon spots inside the raw diamond that needs to be cut out, and it doesn’t leave enough material for an ideal cut.,

Many diamonds are near ideal cut and are amazing, sparkly and shiny. There is no real need for an ideal cut even though it looks nicer. There are plenty of patented cuts like the Tolkowski cut or Heart and Arrows and other styles that are sparkly and lovely just like ideal cuts.


Why Are There Badly Cut Diamonds?

The simple answer is that sometimes diamond cutters will want to preserve more of the gem, to get the maximum carat weight for the diamond. For example, since a 1 carat diamond is more expensive than a portion of a carat, say a 0.90 carat diamond, the cutter might be tempted (or instructed) to make the facets in a way that preserve some extra weight so it would be a 1 carat diamond and fetch a better price.


Why Reflection, Refraction and Dispersion Are Important

Reflection is when light bounces off the surface of a diamond. Refraction is when light enters the diamond and bounces on its interior. Dispersion is the light that exits the diamond. What makes a great diamond is when more light is reflecting inside of it and dispersing from its table, making it sparkle and shine. The better the diamond cut the more it refracts and disperses the light. When it’s badly cut, it may reflect light similar to any shiny surface like a just polished glass; i.e. it only reflects the light. The thing is, when you wear your diamond on a daily basis it may get dirty, and the reflection may diminish, but the refraction and dispersion of a good diamond will shine and sparkle even if the diamond isn’t clean.


A good proportionally cut diamond will sparkle with much less light, while a bad proportion will look like a dull dirty glass.

This is why it’s best to set badly cut diamonds onto necklaces or earrings, rather than your rings or bracelets, since this way they will get less dirty. There’s a saying in the industry that a diamond’s spark represents your love, and a good cut diamond will keep the love sparkle going while a bad one will break your heart. Looking down at the table of a diamond while rocking it back and forth, you’ll notice the most important light dispersion, and also the dispersion from the top crown facets. When you notice the difference between reflection, refraction and dispersion you’ll be ahead of the game compared to most other first-time diamond buyers.


Make Sure to Avoid Fancy Display Lights

Some jewelers will setup a unique display with specially angled megawatt lights to fool uneducated buyers into purchasing badly cut and lower quality diamonds. If you take a badly cut diamond home or outside, it will immediately diminish in looks, especially in how much it shines, compared to what it was in the store. That’s why it’s best to test diamonds in natural light and away from any counters or fancy display lights.


With Bad Lighting You Can Find The Best Diamonds

We already know that fancy lighting may fool you, since you’ll only see the reflection of light, when checking the diamond you’re interested in buying, take it away from megalights and fancy displays.
The megalights shining intensely can make even the poorest cut diamond refract like a king. That’s why it’s recommended to test  diamonds in a poorly lit room, hall or even the bathroom.
If you already have a good quality diamond it will be super easy for you to compare the two in a poorly lit area, and see the differences. Once the light is really bad only the best diamonds will still be able to refract and disperse light.


Easily Identify a Badly Cut Diamond

A smaller well cut diamond may outshine a larger shallow cut as most of the light refracting will disperse from the sides and not from the top table. The same problem will occur when dealing with a deep cut diamonds, where the refracted light will not go up to the eye the way an ideal cut diamond would through the table. After hundreds of years of cutting diamonds, the experts have found the ideal symmetry and proportions that will reflect and refract the maximum amount of light. This is why a great cut diamond will shine and sparkle and show what’s called in the industry fire and brilliance while a poorly cut diamond will not.


The Difference Between a Good Cut Diamond and a Poorly Cut One

Most clients and even some of the experts have no idea what the ratios and dimensions mean, and no GIA certificate will matter if you look at a diamond that doesn’t sparkle. If we have two diamonds with the same color, clarity, shape and weight, how does the layman tell which one is the good cut and which one is the bad cut without spending lots of money?
First take the two diamonds together, and try and look at them together from many angles. Make sure you do this while looking directly down at the diamonds from the top through the table.

If you still can’t figure it out follow these four steps:


Checking for a Good Diamond Cut in Four Steps

  1. Examine the two stones from their sides to see blemishes, scratches or chips; you can use a magnifying tool.
  2. Look at all the facets and try to see if they are symmetrical or if one is a little off.
  3. Check the girdle all the way around from the top and side, to make sure it’s perfect.
  4. Check the culet or the point at the bottom, to see if it’s not chipped or damaged.


Testing for Dispersion – Does The Diamond Explode With Sparkles?

The last test you should be doing is the most important; you must see the diamond’s natural sparkle by testing both stones side by side and determining if one of them has more refraction than the other. If one of them has more shine to it, it’s probably a better cut, closer to an ideal proportion. Most people will only care if the stone really sparkles when rocking it. Most will not even look at other parameters like color or clarity if the stone doesn’t sparkle, but that’s another article all together.


Anyone looking at a diamond will want an explosion of light, not a dull worn-out glass found in the bin.

Some in the industry call it Pizzazz. A great diamond will sparkle, shine and glitter no matter what it’s condition.
After all when we buy a ring we want it to sparkle throughout the entire day no matter what we do, right? A badly cut diamond will just dull out and either break your heart or your wallet, and at times it might be both.


Testing With Your Eyes Rather Than With Tools

When selecting your diamond you need to see with your own eyes how it looks naturally; you do not carry a magnifying loupe everywhere you go, do you? Use a low light or  even a bad light and see the true light dispersion to make your final choice. All the other parameters do not matter, not color, not clarity and not even the price; if the diamond is flawed, it’s a bad diamond and you should avoid purchasing it.


Making a Happy Client at The End

After learning all the techniques we wrote in this article, the clients that bought the bad diamond have returned it, and paid the restocking fees gladly. Then these clients went and tested a new set of diamonds using the methods above and finally found a greatly cut diamond that has fantastic refraction and dispersion.


Testing Diamonds With Vaseline

This test simulates the real life dirt that accumulates on our hands everyday, like soap, dirt, lotions, and so on. What you do is put a pinch of vaseline on the bottom of a diamond and look at it from the top. A greatly cut diamond will still sparkle. The clients I told you about in the beginning of this article really love their new diamond, they “really really love” it as they said; it’s now making them happy forever, sparkling and shining like their love.

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