Chapter 2 - Diamond Education Made Easy (Part 3 - Diamond Structure and HCA Score Calculator)

Now that you're here at Part 3 of my Diamond Education Made Easy, you should now have a basic understanding about the Diamond's 4Cs, and also the diamond certification labs that grades the diamonds. Once you have an overview of the 4Cs, you have a general idea of how you would want your diamond to look, mainly in terms of the colour and size (beauty appreciation with our eyes), and you very much well-armed to tackle the jewelry stores and proceed to the next section on how to choose your diamond ring.

Missed the first and second series? Catch them here so that you'll have a general idea with what I'll be rambling down below.

Chapter 2: Diamond Education Made Easy (Part 1 - Analyzing the 4Cs)

Chapter 2: Diamond Education Made Easy (Part 2 - Diamond Grading System)

But you and I know better, we definitely would like a diamond ring that can give us the most outstanding performance in terms of sparkle and shine. You would definitely want a diamond that sparkles, because what's the use of having a non-sparkly diamond? 

Now you must be asking:

Aren't all diamonds sparkly? They all look fantastic in the store!

Yes, they do. But the lighting in the store is designed to make it sparkle. However, when you bring it natural light, or low lighting, the diamonds loses it sparkle and shine.

Picture obtained from DiamondReview
So which would you choose? 

And that's when things get technical. We're now going to delve deeper into the analysis on the diamond structure, and how it could affect the diamond shine and sparkle. 

But first, you will need to know these three terms:

BRILLIANCE

This signifies the brightness of the diamonds face up. It refers to the quantity of light that is reflected from the surface of the diamond into your eyes. So if the light that enters from above leaks out the back of a diamond, the diamond appears to be less bright.

To view the brilliance, just keep your diamond still under the light. Do not tilt it around. Does it look bright or does it look dull? Are there any dull spots, or are there spots which looks greyish and less bright than the others? This is how you view brilliance. A good diamond should have a good light distribution around the entire surface of the diamond, and should appear very white and bright.

FIRE

The light dispersion from the diamond, that appears as flashes of rainbow colour when you tilt it around. Imagine a diamond as a prism, the white light that enters it gets split into multicolour rainbow lights. This is commonly seen under low light conditions (candle light, restaurants, etc).

SCINTILLATION

In layman terms, this is the sparkle of the diamond. As you tilt the diamond from left to right, you'll see contrasting flashes of white light, mixed with dark. This is the attribute that will commonly attract us as consumers.

In other words, this is what makes the woman go "Ooh, sparkly.."

These three factors will work together to give the diamond its famous appearance, and also  determine how well your diamond performs. Obviously, you'll want the best brilliance, maximum fire and scintillation; because like hello? Who wants a dull non sparkly diamond?

But how do we control these three factors?

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"By Understanding the Diamond Structure and Cut"

Which brings us to Part 3 of my Diamond Education Made Easy series:

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Chapter 2.3: Diamond Structure and HCA Score Calculator

As mentioned earlier, the diamond's cut is one of the most important factors that gives it the attractiveness. But first, we need to have a basic understanding on the diamond cut and proportion. A diamond's cut refers to its facets and angles; their number, proportions, and symmetry, which affect how light reflects out of the stone. If it's cut too deep, or too shallow; the light leaks out from the diamond causing it to reflect less light into your eyes. This loses the sparkle of the diamond. Remember, we always want to maximize the brilliance, fire and scintillation. 

Picture adapted from Ross-Simons

Picture adapted from YourDiamondTeacher

Due to this reasons, that is why diamond grading laboratories came up with a grading system in the 'Cut' section to grade the cut of the diamond. And as I'd mentioned in part 1, we always settle for nothing but Excellent in all grades of cut. 

Yet there must be a range of Excellent in the market. Kind of how they rate you for your tests. If your marks fall within 75-100, it's a High Distinction (HD). But are you within the low category of HD (Around 75 marks range), or are you within the high category of HD (>90 marks).

Of course we insist on the best of the best, the cream of the crop. We want the high category of HD diamonds! So this brings us to the next question: 

But how do we quantify Excellent?

Let me introduce you to the..

Holloway Cut Adviser (HCA) Score Calculator!

The Holloway Cut Advisor is a FREE online tool (Yes we like the word 'FREE') used to find the performance of round cut diamonds based on its potential light return, scintillation and spread. Developed by Garry Halloway, it helps to analyze the proportions using the data of the round diamond (to make sure you're not getting a bad one), and then it renders out a score to get the diamond cut quality.

Typically, the information that this calculator uses are:

1. Total depth: Length of the diamond
2. Table: Diameter of the flat surface (when viewed from top)
3. Crown angle: The angle of the top half of the diamond
4. Pavilion angle: The angle of the bottom half of the diamond
5. Culet: How pointed the diamond is 

You can get all these information from the diamond certificate (AGS, GIA, etc). In fact, you could even key in your diamond certification number, and they'll extract the information for you. Key it in at the selection screen at the Pricescope HCA Score Calculator page:

Picture adapted from Pricescope

The page will then show two results and outcome: First is the HCA Rating number, and also a colour contour graph.

So how do we analyze the score?

What we are concerned about now is just one main part:

The HCA Rating

The output from the tool will generate a 0-10 score, with lower scores indicating a better cut quality. Typically, we're looking at a score of 0-2 as they represent the high performing excellent diamonds. This means that the diamond that have a HCA score of 0-2 is within the ideal proportion range, which is predicted to give an excellent light performance. 

Take a look at an article by Beyond4Cs to view the difference between a 1 carat diamond with a HCA score of 1.2 (Excellent), and 3.6 (Very good).

Pictures and research are all done by Beyond 4Cs 

Both diamonds have the same size of 1.0 carat, with similar cut, colour and clarity specifications. The only difference is that the diagram on the left represents a diamond with a HCA score of 1.2 (Excellent region), while the diamond on the right represents a diamond with a HCA score of 3.6 (Very Good region). From Idealscope image (the red image), there is a pale white circle surrounding the diamond table, which represents light leakage. Therefore even though they have the same 4Cs, they will still perform differently as the diamond on the right does not have the 'ideal' proportions compared to the diamond on the right.

Other results that are also published together are: 1) the individual grades for the Light return, Fire, Scintillation and Spread with grades of Excellent, Very Good, Good, Fair and Poor. It'll be best to have all of these factors in the Excellent range. 2) Colour coded chart which indicates where the diamond falls within the proportion chart.

So when to use the HCA Tool, and what are the Limitations?

This method is an excellent way to weed out the low range of HD diamonds. However, I must emphasize that this is not a selection tool, but rather it is a rejection tool to reject the low performing diamonds. It is best that you do not use this method to select your diamond, because it does not take into account all the facets available on the diamond. It only takes a small proportion of them, and produces the score that represents the average light performance and cut of the entire diamond.

There are many articles that explains the limitation of HCA Tool, which I'll link it here for further readings:

Beyond4Cs: Is the HCA Score Always Reliable For Diamond Selections?

Prosumer diamonds: Holloway Cut Adviser (HCA)

Conclusion

In summary, all that you need to know are the following:

1. What is HCA Score and what's the representation of HCA Tool
2. The HCA rating should fall within 0-2 to give you a better probability of finding a diamond with the best proportion for maximizing brilliance, fire and scintillation.
3. HCA Tool should be used as a rejection tool to eliminate the lower grades from the excellent cut diamonds

When you reach the end of this article, you should have a very brief understanding of HCA score, and how to use this method when you look for diamonds at the jewelers. 

For a more detailed understanding of HCA score, you may read an article by GoodOldGold - A Consumers Guide to HCA. I highly recommend this article, as I find it a very interesting read, with lots of pictures and explanations.

In Part 4 for the Diamond Education Made Easy series, I'll be discussing on the significance of Hearts & Arrows on the optimal symmetry of the diamond. Go forth and continue your diamond education journey!

Chapter 2 - Diamond Education Made Easy (Part 4 - The Significance of Hearts & Arrows)