Cut is the single most important of the 4Cs when it comes to buying diamonds. Yes, it’s delightful to see a monster-carat sparkler twinkling at the world from your ring finger. The thing is though: if the cut is poor, it won’t sparkle, no matter how big the carat, how perfect the color, or how excellent the clarity.

With that in mind, we’re here to help you spot the difference between a well-cut diamond, and a poorly-cut dud. Because trust us, even with all the love and romance in the world, a non-sparkly diamond can really sap the spark out of a proposal!

Fire, Brilliance and Scintillation

Let’s start with the benefits of a well-cut diamond, and what it should look like.

A well-cut diamond is luminous in its beauty, and quite obviously reflects white and colored light back to your eyes. A poorly cut diamond, on the other hand, is a thing of despondency. Dull where it should be brilliant. Lightless where it should shine and sparkle. More than this:

  1. A well-cut diamond will reflect more light and appear larger than it actually is.
  2. The face-up color (the color when looking at the diamond from the top down) of a well-cut diamond will also look brighter.
  3. An ideal or excellent cut can even mask or camouflage inclusions (small imperfections or flaws) in the diamond, thanks to the greater brilliance, fire, and scintillation afforded by excellent craftsmanship in the cutting.
  4. A well-cut diamond has “fire”: this is the light dispersion that looks like flashes of the rainbow. (Fire, if it exists in your diamond, is especially visible in dim lit environments… like romantic candlelit dinners, hint hint!)
  5. A well-cut diamond has “brilliance”: this is the light which is reflected in and out of the diamond. The perfect proportions of an “ideal cut” prevent light leaking out the bottom or sides of the diamond, instead reflecting straight in, and then loop straight back up and out the top, with a resultant much brighter sparkler!
  6. A well-cut diamond has “scintillation”: this is the pattern of dark and light facets that causes the mesmerizing sparkle of your diamond as your hand moves, mostly seen in well-lit environments (like the office, which is handy for complimentary oohing and aahing #justsaying).

All of these – sparkle, brilliance, fire, scintillation, hidden flaws, brighter color – far outweigh size when it comes to dressing that ring finger with something impressive. Sparkle far outweighs size; brilliant is better than big; dazzling beats dull.

Shape vs Cut

Now let’s move on to cut itself, and the various grades of cut in the world of diamond dealing.

But first, quick note: cut is different to shape. Diamond cut doesn’t refer to the shape of the diamond – think oval, heart, square or pear shaped. Where the shape of a diamond refers to the outline or external figure of the diamond, cut refers to how well the diamond is cut and polished from the rough stone, paying special attention to the proportions, facets, dimensions, depth, symmetry and reflective qualities of the diamond.

Shallow Cut

In simple terms, when a diamond cut is too shallow, the light travels through the diamond and exits through the sides, instead of reflecting through the top of the diamond and to your eyes. (It is slightly more technical than this, with words like pavilion, crown, table etc thrown into the mix, but we don’t need to go into all that detail!) Shallow cut diamonds might look impressive because they seem big and bold based on their size and breadth (fun fact: shallow diamonds are sometimes called ‘spready diamonds’ because they spread sideways), but their brilliance, fire and all-round sparkle is significantly less so!

Deep Cut

When a diamond is cut too deep, light eventually passes through the bottom of the diamond, thus completely losing all the brilliance, vibrance and radiance that makes diamonds so magical. No light is reflected back to the viewer’s eyes. No light, no delight. Ultimately, this can also make the diamond look smaller.

Ideal Cut

Ultimately, a well-cut diamond maximizes the light that strikes each of the important parts of the diamond, which means that the light reflects back to the eye, rather than escaping through the sides or the bottom.

The best cut is graded as either “excellent” (by the GIA) or “ideal” (by the AGS), which indicates that the cut is well-proportioned with optimal facet angles, allowing the brilliance, sparkle and shine to pass through the diamond and out into the world for all to see.

So, why might a diamond be poorly cut, if the benefits of an ideal cut are so patent? A couple of reasons:

  1. The diamond cutter might have been dealt a rough stone that wasn’t great to start with. There could have been a big carbon spot that occurred in the wrong place for optimal cutting;
  2. The diamond cutter might have been trying to preserve as much weight in the stone as possible, to fetch a greater price for the greater weight/diamond carat;

Whatever the reason for a poor cut, it helps to know how to spot the signs and to remember that size isn’t everything when it comes to diamonds – sparkle is where it’s at!

Spot the Signs


Move away from the fancy, flashy display lighting! The jewelry counter often has special lighting installed, designed to make everything look positively magical! So much so that even poor quality diamonds can be made to look Grade Amazing under mega-wattage overhead lighting.

Bottom line? Examine the diamond under natural lighting. Poor quality diamonds can look beautiful under great lighting, but under poor light they’ll show their true colors. No amount of ugly lighting, however, can diminish the dazzle of a beautifully cut diamond.

Check for Chips

Using the naked eye, AND a jewelry loupe, check the diamond from all sides for imperfections, chips and scratches. And don’t forget to check the pointy bottom part of the diamond: make sure it’s not chipped or broken!

Also be sure to check the girdle (the widest part or the circumference) of the diamond to ensure that it’s perfect all the way round, as well as the facets and proportions for evenness.

Use Your Eyes

A jewelry loupe is all well and good to look for imperfections and flaws, but your eyes won’t tell lies. If the diamond sparkles and flashes under natural lighting, it’s likely a better cut stone. Does it remind you of sunlight or a lump of glass? Is it dazzling or is there just a hint of “dull”? Trust your eyes, they won’t lie.

Choose a Trusted Jeweler

Of course, if you choose your jeweler wisely, poorly cut diamonds are immaterial. You won’t find one. At Keezing Kreations we will help you choose the very best diamond for your budget, paying careful attention to ensuring all four Cs are up to the task of delighting with their dazzle.


At Keezing Kreations we have decades of experience choosing only the best quality diamonds that showcase the sparkle, brilliance and shimmer that life’s biggest moments deserve! With the finest quality diamonds in Boston, in all shapes and sizes at very competitive prices, and 40 years’ experience creating custom jewelry items designed to spark both sparkle and joy, you can trust our jewelers to help you find the diamond of her dreams.

Contact us today: Call 617-650-9934 or email