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Diamond Symmetry: How It Affects Diamond Properties

Diamond Symmetry: How It Affects Diamond Properties

You’ve undoubtedly heard bits of chatter regarding diamond quality and the 4C’s that portray it. The cut is deemed the most important since it affects all others – but what has it to do with diamond symmetry? 

What does diamond symmetry refer to, and is it conditioned by the internal structure of the gem as well? The answers may surprise you! 

So, keep on reading because we’ve aligned the answers to these questions – and some more – in perfect symmetry!

Diamonds: Internal Structure 

Often there’s talk about symmetry achieved when modeling the diamond facets, but that would be pointless if the inside of a diamond didn’t hold certain symmetry, as well. 

All that’s needed for a luster diamond is a thread of light. These light waves “play” against the stone’s internal planes in three ways:

  1. Brilliance – Deemed the most important, it relates to the white light rays and the way they’re directed once they enter the stone. The goal is to have them come in from any angle but exit the stone swiftly at the top of the jewel – in the viewer’s line of sight. 
  2. Fire – Diamonds display “fire” better than any other material. That means shining in a flame of differently colored, dispersed wave-lengths that separate individually after a primarily white light that they cumulate in bounces off a few times amongst the inner planes. These waves then find some way out of the center of the stone and reach the viewer’s eyesight. 
  3. Scintillation – Although the public might not be aware of this, scientists believe it’s most creditable for the diamond shine. Flashes of light appear solely when the gemstone, the viewer, or the light source are moving, and it seems like they’re skipping. These flashes can be white or colored – which is the reason why there’s color trapped inside the gem. 

Cutting is indeed commendable for these light shows, dictating the direction – and the way – the beams move, and we’ll get to that soon enough. 

However, that would never be possible without the atoms that a diamond consists of – carbon. They’re the ones constituting a diamond inside and out – and photons that make these light rays interact with them!

There are so many interesting facts about these amusing reflection phenomenons – but we have covered them all in separate guides. So, we won’t be getting into the details here. With that said, let’s find out what hides inside a gem – besides the light! 

What Are Natural Diamonds Made Of?

Here’s a bit of chemistry: Carbon is a nonmetallic chemical element, and even though it’s widespread in nature, it’s not as plentiful and makes only 0.025% of Earth’s crust. You’ve probably heard that it’s present in coal, and that’s actually how it got its name – from the Latin word “carbo.” 

Still, it’s a known fact that carbon can form more compounds than all other elements combined, with one being indeed familiar – diamonds!

Diamonds Are Crystals

There would be no gemology without physics, too! Diamonds, graphite, and one other substance present the only form of elemental carbon, and they all have a crystalline structure.

That means that carbon atoms are arranged in a specific repetitive manner in space – and that’s the main difference between the two. Think of it as a 3-D model of all the atoms bonded to each other in the same way in the form that’s called a lattice. 

A small fragment of this repeated entity can be referred to as a unit cell. It’s the smallest building block that defines how the gem as a whole will appear.

Lattice parameters of the combined unit cells are essentially the lengths of their edges and the angles between them, and they can be represented as mathematical vectors. These vectors define the internal symmetry of a diamond and, consequently, which atoms will interact with light photons and in what way.

How do we know what they look like, though?

Vectors of the carbon unit cells that a stone consists of can become visible by X-ray diffraction. The rays diffract in different patterns – depending on the vector direction. 

These variances are made by different arrangements of atoms within a diamond, which makes a diamond’s structure as unique as a human fingerprint. That’s one of the key reasons why there are no two gemstones that are alike!

So, how are they arranged?

They’re always arranged tetrahedrally. Each carbon atom is covalently attached to four other ones with a 1.544 x 10-10 m distance and an angle of 109.5°, constructing a rigid, infinite net as previously described. These atom bonds are tight in diamonds and make them the hardest known material to date!

On the Mohs scale of hardness, they’re the only mineral that ranks a perfect 10! The testing method is based on making sure that one can make abrasions on a smooth surface – rather than the “chalk” marks that rub off the gem. 

That’s the primary reason why diamonds can be damaged solely by another diamond and are able to scratch every other material you could think of right now.

Their internal symmetry also makes them extremely durable, greatly resistant to compression, and the best heat conductor there is. These precious stones conduct sound but not electricity – and have remarkable optical transmissivity and chemical inertness.

On the other hand, they could break pretty easily. Sometimes, even falling at an inconvenient angle is enough to cause a chip – if there are inclusions present within the diamond, that is. 

These inclusions are natural, pre-existing imperfections within diamonds. Moreover, there’s a thing called a diamond strain – a buildup of pressure formed while the diamond was created. One direct hit could be enough to “release” that strain by – well, breaking the diamond.

And if you’re interested in learning about the safe-keeping of your gems, be sure to check out this article. We’ve discussed some important aspects of protecting your diamonds there.

Related Read: Anatomy Of A Diamond: Everything You Need To Know

What Is Diamond Symmetry?

Now that you’ve learned more about how the symmetry looks inside of a diamond, it’s time to move on to the gem’s surface. 

You probably know that the diamond surface takes the form of planes called facets. They don’t come naturally to the gemstone and a skilled diamond cutter has to create them by cutting and, in that manner, directing the light rays so that they exhibit a maximum play of light. 

It can be done by hand or by a machine – and nowadays, you can create many exotic diamond shapes this way. 

Speaking of diamond cuts, you might be interested in the fact that the round brilliant diamonds take the cake in terms of their perfectly optimized, sparkling shape.

Cutting and polishing are the two finishing touches of the whole diamond sculpting process, and the GIA considers specific diamond features of these steps, viewed under 10x magnification. 

And it all comes down to symmetry! People usually think of it as shape, but it’s something else entirely: It refers to how well the facets of the stone are aligned, which impacts the grade and the price of a diamond

That’s why any visible mistakes in facet positioning and shape must be documented, and they’re often served as cumulative instead of singular deviations. If you were wondering, here are some typical symmetry flaws you might come across when shopping for a diamond: 

  • Extra Facet (EF) – An unrequited facet that’s been added
  • Misalignment (Aln) – Crown and pavilion facets displaced 
  • Table/Culet Alignment (T/C) – Culet and table placed in different directions
  • Natural (N) – A part of the original diamond surface left untreated
  • Out-of-Round (OR) – Deviations of the circular shape
  • Pavilion Angle Variation (PV) – Unequal pavilion angles
  • Table Off-Center (T/oc) – Deviation of the table 
  • Uneven Outline (UO) – Bumps and flattened spots as a result of natural, extra facets, or uneven girdle faceting

There are a dozen more, and when you look at a diamond certificate, they’ll usually be listed as “symmetry features” – if there are any, that is! 

Diamond Polish   

Diamond symmetry wouldn’t be as effective if there weren’t a final touch to amplify the desired light show – and that’s where diamond polishing comes in:

Important as the cutting process itself, polishing is responsible for achieving the glass-like finish you’re used to seeing on a gem’s surface and, as such, provides maximum entry and exit points for the light rays. 

It was commonly done using polishing wheels and diamond dust – but it’s now deemed that such a mechanical process often leads to subsurface damage and limits the achievable surface finish of a stone. 

Don’t you worry; GIA has listed those “shortfalls,” as well:

  • Nick (Nck) – A notch on a facet junction 
  • Lizard skin (LS) – An uneven texture of a single facet
  • Pit (Pit) – A tiny hole appearing as a white dot
  • Burn (Brn/Dop) – Whitish haze caused by heat 
  • Abrasion (Abr) – Scratches and pits forming fuzzy facet junctions instead of sharp lines

There are a few more – and they’re all called polishing features. Their location is listed, as well, since they can appear on any part of the gemstone. That’s why scientists are looking into new physical and chemical means to replace (or improve) the standard polishing process. 

But since there’s no single method to address all of the requirements for a perfect polish, there’s always a possibility of re-polishing, and it’s often been used on vintage diamond pieces, such as old single, Peruzzi, and rose-shaped diamonds

You can find out more about such vintage cuts here.

Symmetry Or Polish: What’s More Important?

Cutting the diamond asymmetrically can cause the light rays to move in all the wrong directions – at inadequate angles that make the stone seem dull. 

And since it’s common knowledge that the cut determines the rest of the 4 C’s, poor symmetry can, indeed, have a very visible effect. 

But we can’t blame it all on the artisans, considering diamonds come as they are. 

On the other hand, polishing has a more direct impact on the gemstone – and imperfections can barely be viewed by the naked eye. So, if you have to choose between the two when shopping, the diamond’s polish would be the “correct answer” here. 

Still, they inseparably determine how bright the stone will shine – and that’s why they’re usually graded together!

The Grading System 

The GIA’s reputable grading system for symmetry and polish combined looks like this:

  • Excellent – Facets perfectly sized and proportioned
  • Very Good – One or two disproportionate elements
  • Good – Size or location of facets is disproportionate, and sparkle is affected
  • Fair – Visible disproportion in facet proportions that affects brilliance greatly 
  • Poor – Visible disproportion in facets that misdirect the light rays, causing the loss of sparkle and brilliance

Learn More: Diamond Proportion: Everything You Need to Know

Gemologists say there’s little difference between the top two and they can both be considered an Excellent cut. That said, if you strive for perfection – well, then think of a round brilliant gem!

It might rank a GIA Triple Excellent or an AGS 000 grade, which stands for Excellent/Ideal cut, symmetry, and polish. 

Heck, it might even be a super-ideal that costs up to 35% more than an Excellent graded piece, and its symmetry and polish create a hearts-and-arrows pattern – with arrows being visible from the top and hearts seen from the bottom of the precious stone. 

But even these aren’t always noticeable once the stone is set in jewelry. That’s why you should find the rest of the details about GIA certificates and others here.

Learn More: Diamond Cut Grade: All You Need To Know About Diamond Cut

Final Thoughts 

Natural diamonds are made of pure carbon but can have some trace elements that add color to their luster. All these atoms are tetrahedrally arranged in space and make the internal structure that reflects light in a specific color – or none. 

But diamond symmetry is responsible for taking advantage of these light angles and directions through that structure. It’s accomplished mainly through cutting and arranging diamond facets – but it’s greatly enhanced by polish.

When combined, the internal and external structures achieve the most favorable sparkle within a diamond. So, please keep both in mind when purchasing a certified precious stone!