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Diamond Grading: What You Need to Know

How are diamonds graded?

How are diamonds graded? Why does it matter? How impartial is the process? What if a diamond is graded incorrectly? Are lab diamonds graded the same way as natural diamonds? This and more, below.

After a diamond is cut, it’s graded. Grading laboratories not only screen for the type of diamond (lab vs. natural) but they evaluate the diamond for a range of quality characteristics such as cut, color, clarity and carat, as well as more detailed measurements such as girdle thickness, crown angle, and pavilion depth. The grading report generally includes three sections: the four c’s, the diamond measurements, and a plot map detailing the type and location of any inclusions.

Diamond’s are graded blind, meaning without names, logos or brand references which could result in favoritism. Two to three diamond graders review each stone and only when there is sufficient agreement and alignment on the grade of the diamond is a report generated.


The Grading Process

Step 1: Carat

When a diamond arrives at a lab, it is first weighed, using an electronic micro-balance. Next, it is 3D scanned to determine it’s measurements, proportions, and angles.


Step 2: Authenticity

Next, the diamond is analyzed for authenticity, to determine if the diamond is a mined, lab-grown or color-treated. As lab-grown diamonds have risen in popularity, this process has become essential.


Step 3: Clarity

The diamond’s clarity is graded by eye, and under 10x magnification by multiple graders. They evaluate the diamonds polish, symmetry and clarity, and in some cases create an entire plot map of inclusion types and locations. They look for evidence of artificial treatments which impact the value of the diamond.


Step 4: Color

Again, multiple diamond graders evaluate the color of the diamond against a set of master stones ranging from D (colorless) to Z (yellow). The grader goes stone by stone until they find a match. They also review the diamond under UV light to asses fluorescence — the blue glow fluorescent diamonds emit under UV.


Step 5: Cut

Finally, a cut grade is assigned. This grade takes into account the diamonds proportions, brightness, fire, scintillation,  polish, symmetry and more. The cut is the number one thing quality characteristics that determine a diamond’s sparkle, and is the most important of the four C’s.

While the standards from diamond grading are rigorous and mature, in many ways, it’s as much art as science. If you’ve ever squinted, looking at a G color round brilliant next to an H color round brilliant and wondered if they are the same color, you’re not alone. While diamond graders are highly skilled and go through rigorous training, grades can vary from person to person and lab to lab and inform the price you pay, the cost of your insurance, and ultimately the diamonds resale value.


Who are the leading diamond labs?

If you’ve tried to buy a diamond you’ve most likely come across an article that starts: the only reputable diamond lab is the GIA. As a rule of thumb for mined diamonds, this rule holds up. There’s more then enough GIA certified mined diamonds on the market, so unless you have something particular in mind, there’s not a good reason to look elsewhere.

Beyond that, there’s a long list of reasons to trust the GIA. Established in 1921, the GIA is the leading gemological institute in the world. Not only are they known for having the strictest grading policies amongst all the labs,  but they created the Diamond 4Cs and the International Diamond Grading System™ — the global standards that are used to determine a diamond’s quality and authenticity. The two factors that ultimately determine a diamonds price, and value. They are more than fourteen locations and have trained 365,000 since their founding. To say they know diamonds and gemstones would be an understatement. For these reasons and more, Frank Darling exclusively sells mined diamonds graded by the GIA.


Lab Diamonds

While other leading gemological laboratories have readily embraced lab-grown as an equal, affordable and sustainable alternative to mined diamonds, the GIA has not. As the popularity of lab diamonds have grown, the GIA’s position has remained relatively unchanged.

While the GIA does grade lab diamonds, they grade them with much less stringent guides then mined.  The GIA does not give specific color or clarity grades, and instead uses ranges to articulate the diamonds make. Instead of assigning a D color grade, they assign a D-F grade defined as “colorless.” This lack of specificity effects the price and value of GIA graded lab-diamonds.

Under mounting pressure and a recent change in legislation from the FTC, the GIA announced this month that they would no longer refer to lab-grown diamonds as “synthetic” on their reports but as “Laboratory-Grown Diamonds.”

While the  intent is to avoid consumer confusion, the reality is that consumers purchase lab-grown diamonds similarly to mined diamonds, with a distinct preferences for cut, color, and clarity, and the report is misleading and insufficient particularly when a “D” color grade diamond can sell for hundreds if not thousands more then it’s “E” counterpart.


So where does this leave us?

Graded Lab Diamonds

IGI and GCAL and have stepped up and stepped in to fill the gap, recognizing that lab-grown diamonds aren’t a passing trend, but a rapidly growing part of the overall landscape. All Frank Darling lab diamonds come with an IGI or GCAL certificate of authenticity based on an internationally recognized trading system. Diamonds analyze each diamond by eye, and with state-of-the-art equipment to guarantee authenticity.

GCAL goes one step further to analyze each diamond using its proprietary Direct Assessment Light Performance analysis. This method analyzes each diamonds light performance and generates a much more in-depth report. GCAL goes as far as to offer a cash back guarantee which protects the consumer in the event of an error.


Non-Graded Lab Diamonds

One only has to do a quick search on Alibaba to find a long list of non-graded lab diamonds or lab diamonds with misleading language or even worse, falsified grade reports. Synthetic diamonds being mislabeled and sold as “lab diamonds” or even “natural diamonds” is a growing and worrisome trend in the industry. While one could choose to purchase these diamonds, the risk of inauthenticity and inaccurate grading is real.


Cut on Demand Diamonds

One of the unique services Frank Darling offers is the ability to have a custom cut diamond. Because we have access to the rough lab-grown cores, we can cut virtually any diamond shape and size from the quality and clarity rough of your choosing. After we cut the diamond, we send it to GCAL or IGI for certification. This service allows you to get a truly unique and one of a kind diamond— this could be an odd-size Asscher, a rose cut or a Marquise, many of which are difficult to source and find.