Beyond the 4 C’s
GIA Guest Lecture Featuring Ada Diamonds Founders Lindsay Reinsmith and Jason Payne
Topics We Covered
- Differences between lab and natural diamonds
- Color tinges
- CVD diamond growth and BGS (brown, gray, strain & striations)
- HPHT diamond growth and BGP (blue, gray, phosphorescence)
- How and why crystal defects occur in lab diamonds
- How these defects are measured and determined
- Why you should care!
Overview of Lab Diamonds vs Natural Diamonds
Lab Diamonds Have Fewer Impurities
There are Two Ways to Grow Lab Diamonds:
The quality of the best lab diamonds exceeds the quality of the best natural diamonds.
Ada’s lab diamonds are some of the most sensational on earth.
How Did We Get BGS and BGP?
At the start of the commercialization of lab diamonds, there was a strong desire to produce a product indistinguishable from natural, but with higher purity. Over the last 3 years, the lab diamond industry has seen an explosion in demand as well as a significant increase in the number of CVD growers around the world. Nascent, aspirational growers purchased disadvantaged tech reactors to get in on the action. People who had no business being in this business entered the market, and many of them still don’t know what they’re doing.
The manufacturing side of diamonds couldn’t get enough. COVID-19 disrupted diamond mining far longer than it disrupted diamond growing. Existing CVD growers began getting pressured (pun intended) to produce more and more with their existing equipment without reinvestment. The goal: produce as much as possible for as cheaply as possible.
Sentiments like these harm consumer confidence in lab grown as a whole. But there are absolutely stunning and gorgeous lab diamonds out there that aren’t gray and aren’t brown. Consumers deserve that information and transparency to make better decisions.
Chemical Vapor Deposition(CVD)
In evaluating CVD diamonds, we recommend looking for BGS:
B = Brown
Brown hues in CVD diamonds can be more of a pinkish brown or more grayish brown. Both of those diamonds are from the same grower! Brown tinge also occurs in natural diamonds, though the reason for brown in natural diamonds is sometimes due to a completely different type of defect (plastic deformation).
In CVD diamonds, brown is caused by two main things:
- Empty voids in the diamond and
- Nitrogen atoms trapped in the crystal.
Nitrogen defects can be accidental, leaking into the reactors past faulty seals, or nitrogen can be intentionally added as a catalyst to speed up the growth process.
Both F Colors
So What Do You Do When Polycrystalline Forms?
You stop your machine, take the crystal out, laser off the polycrystalline layer, and put the diamond back into the reactor. What forms: striations.
The impact of starting and stopping the CVD reactor are rings of diamond growth known as striations. Nearly all CVD diamonds have some striations, it’s not a binary.
The image at left shows 8 growth cycles, designated by obvious rings. It’s not just the presence of these growth rings. How far apart or close together the rings are represent a timetable showing how long the growth cycles lasted in between stops. Striations can make a diamond look out of focus and lackluster.
Gray & Striation Case Study
This was a G color CVD diamond we sent for additional analysis to GIA’s researchers. It has a very obvious gray tinge. After spectral analysis, we concluded this was likely due to a combination of silicon defects and graphitic nano inclusions. The silicon and silicon vacancy defects were too significant to have been from the CVD viewing glass, and were likely the result of intentionally added silicon during growth. The zoning and clear growth line (shown in bright green) indicate that this diamond was likely moved from one reactor to another generation CVD reactor with a different chemistry profile. It’s possible one of the reactors was being used for R&D purposes.
High Pressure High Temperature (HPHT)
In evaluating HPHT diamonds, we recommend looking for BGP:
Blue is Variable
During HPHT growth, you can have some diamonds that are blue and some that aren’t, and even within the diamond you can have some parts of the diamond that are blue and some that are not.
This is the spectral analysis of a single grower of HPHT. You can see in some cases the boron spikes are very low and in others quite high. Even though nitrogen is more likely to be dispersed throughout a diamond’s crystal lattice, boron can be growth sector dependent and quite concentrated. In other words, boron is very difficult to control.
This type of boron zoning would not be present in a natural Type IIb diamond.
Green Tinge Case Study
In some cases you can have both a growth sector of nitrogen and a growth sector of boron. In this case, this greenish tinge pear had both, resulting in blue + yellow = green. Despite having enough nitrogen to modify the color, this HPHT diamond is still Type IIb based on the boron content as there is more boron than nitrogen. This is NOT a high enough concentration to be a fancy color diamond. It received an “I” color grade.
There are lots of reasons why HPHT can look gray. For some, it’s simply that it has a blue tinge that looks gray in certain lights. Others can be irradiated or have elements like aluminum, titanium, nickel, or other trace metals. Some can have metallic inclusions.
The exact formulas that keep out nitrogen are tightly held trade secrets. Those secrets can determine if HPHT diamonds are grayish blue or bright white.
Gray Tinge Case Study
This is a fascinating diamond we shared with GIA. In our conversations with GIA researchers, we’re not 100% certain why it has this super obvious gray tinge. One theory is that it’s due to the presence of growth tubes, seen here under SW light as uniform streaks or claw marks. This diamond is also Type IIb, had strong phosphorescence, but does not appear blue in person. This is honestly one of the ugliest lab diamonds we’ve ever seen. Super interesting.
- an orange or blue glow seen in a diamond after exposure to long wave UV light, sunlight, or full spectrum light bulbs
- not the same thing as fluorescence
- due to boron, but it’s not necessarily seen only in blue tinge
- able to make a diamond look hazy or milky in low light environments
- able to last for a few seconds or several minutes.
We’re only discussing phosphorescence under long wave UV light and sunlight. Shortwave light is filtered by our atmosphere and using it at high power can be dangerous and should only be done by trained professionals.
I have personally inspected over 15,000 certified lab diamonds above 1 carat. I’ve seen diamonds from over 100 growers and 10 different countries. I look at lab diamonds side by side every week. And I’ve been documenting and cataloging my assessments over the last seven years.
The breadth of quality I’ve seen makes me uniquely qualified to speak about this product and what consumers should look out for. Despite my exposure and expertise, I would never, ever, ever buy a lab diamond totally sight unseen. And I don’t recommend that you do, either.
I want to remind the public that lab diamonds are, fundamentally, superior to natural diamonds in their crystal purity. There is no denying that. Beyond purity and the 4 C’s, there are lab diamonds that rival the absolute best natural diamonds in the world. Impeccable crystal material, bright white shine, and near perfect cut.
But there are also lab diamonds out there that are defective enough to make you question if it’s a diamond at all.
How consumers can protect themselves:
1. Work with a jeweler that you trust.
2. Don’t rely simply on a grading report or a low resolution video.
3. Compare lab diamonds side by side.
4. And when it comes to price, if it seems too good to be true, it probably is.
-Lindsay Reinsmith, Founder, Ada Diamonds