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Do Lab Created Diamonds Test as Real?

The answer to the question everyone wants to know. If my lab-created diamond is tested on a diamond tester — will it pass.

What Lab Diamonds Aren’t

Lab diamonds are not stimulants. Cubic zirconia and moissanite are simulants – lab-grown diamonds, are, as the name suggests, diamonds. They have the same chemical, physical, and optical properties as mined diamonds much to the mining industry’s chagrin. Unlike diamond simulants such as CZ or Moissanite, lab-created diamonds will test positive when using a diamond tester. This is because, we’ll repeat it, they are diamonds. According to both Frank Darling and the FTC, your diamond is a diamond whether it was created in a lab or not.

Now that’s out of the way, let’s move on. From time to time a salesperson on the internet will claim to be able to tell the difference between a mined diamond and a lab-created diamond while providing limited details on how they achieve such a miraculous feat. 

There are three physical differences between lab-created and mined diamonds. None of these differences have an effect on the integrity, optics, or beauty of the diamond. Brace yourself; this is going to get technical.

What Lab Created Diamonds Are

A range of 1.7 – 2.1 carat lab grown
emerald cut diamonds

Lab diamonds are diamonds, period. They are sparkly, envy-inducing, conversation-starting chunks of carbon that we, as humans, can’t seem to get enough of. In 2018 the FTC ruled, “The Commission no longer defines a ‘diamond‘ by using the term ‘natural’ because it is no longer accurate to define diamonds as ‘natural’ when it is now possible to create products that have essentially the same optical, physical, and chemical properties as mined diamonds.”

But, there are some key differences, one in particular which can cause a lab diamond to register as Moissanite on a Moissanite tester. Curious yet? Read on.

What are HHTP Diamonds?

There are two main types of lab grown diamonds. The first and oldest, HPHT, stands for high pressure high temperature. The process mimics the natural conditions that form diamonds in nature. Diamonds grow in as little as two weeks.

The Drawbacks of HPHT Lab Grown Diamonds

Funky Tinges

HPHT diamonds can exhibit a yellow, brown or blue tinge.

Metallic Inclusions

HPHT diamonds sometimes contain metallic inclusions. Under magnification these inclusions look like black hairs. This is flux. It’s a magnetic relic of the growing process. While flux won’t hurt the integrity of your diamond, we recommend looking for a diamond without it.

Flux can be reflective since it’s metallic. Credit: GCAL

Flux under extremely high magnification. Credit: GCAL

Failed Tests

HPHT diamonds can register as moissanite on inexpensive moissanite testers. 😱Basically, a moissanite tester measures how (and if) a stone conducts electricity. Moissanite does, diamonds don’t. Unless they’re type 2b. Don’t you love all these exceptions! Naturally blue diamonds are type 2b. So are some HPHT lab grown diamonds. This happens when boron gas enters the growing chamber and causes what’s referred to as “Blue Nuance.” Boron conducts electricity tricking the tester into a false positive.

While this isn’t a reason not to buy an HPHT lab-grown diamond, if it concerns you, opt for CVD.

What are CVD Diamonds?

CVD stands for chemical vapor deposition. CVD diamonds grow in a vacuum chamber pumped with methane gas. Romantic, isn’t it?

How Are CVD Diamonds Grown?

CVD diamonds are grown with a carbon wafer cookie and a chamber full of gas.

First, a technician places a diamond seed in the chamber. These seeds look like very tiny wafers.

Second, the chamber is pumped with methane gas.

Third, a laser or microwave beam is used to break down the gas. As the gas breaks down, carbon atoms fall onto the diamond and crystalize. Romantic isn’t it?

Finally the technician removes the diamond from the chamber and cuts away its black coating, revealing the white rough below.

The Drawbacks of CVD Lab Grown Diamonds

Notice how the oval diamond is more yellow, whereas the princess cut diamond is more pink. This is a tinge.

Funky Tinges (Again)

Similar to HPHT grown diamonds. CVD diamonds can exhibit colored tinges and is difficult to master.

Internal Graining

CVD diamonds can also have a unique graining pattern that is visible to the eye.

Exotic Inclusions

CVD diamonds often contain black inclusions. These come in the form of clouds, crystals and pinpoints often clustered on one plane.

A flat cloud of black inclusions seen in a CVD diamond. Credit: GCAL

A single sharp plane that appears in CVD diamonds. Credit: GCAL

Can you Tell if a Diamond is CVD or HPHT?

CVD and HPHT diamonds, for all intents and purposes, are identical. A diamond is a diamond, remember? Sometimes the growing process is listed on the cert, other times it isn’t. If this is the case, it’s nearly impossible to know which process was used to create the diamond.

If you’re particular about the process with which your diamond was grown, it’s best to work with an expert. We have direct relationships with major HPHT and CVD diamond growers in the US and abroad, and are happy to source whichever type lab diamond you prefer direct from the source.

Three Ways Lab Diamonds Differ from Natural Diamonds

1. Lab Diamonds are a Different Type of Diamond (Mostly)

Experts group natural diamonds into two main categories — type Ia and type IIa

Type Ia diamonds contain nitrogen; type IIa diamonds don’t.  

Fun fact, nitrogen is the most common impurity in diamond. It accounts for up to 1% of a type Ia diamond by mass. It’s the main reason that some diamonds sport a yellow tinge.

In contrast, lab grown diamonds grow in a highly controlled nitrogen starved environment. This mostly results in a different type of diamond — type IIa. Type IIa diamonds can occur in nature, but they’re very rare, and highly valuable. Only 5% of mined diamonds are type IIa.

A diagram illustrating the structural difference between type 2a and type 1a diamonds

2. Lab Diamonds are Grown in a Lab, Duh

There are two ways to grow diamonds in a lab.

HPHT, which stands for high-pressure-high-temperature, and CVD, chemical vapor deposition. Let’s talk about HPHT first.

3. Lab Grown Diamonds Come in a Different Shape than their Natural Cousins

In nature, diamonds form over a long period under high temperatures. These two factors result in this unique octahedron shape. You might be thinking, what’s shape got to do with it? Well, while the rough diamond shape doesn’t impact a diamond’s material properties or beauty, it does change which diamond shapes is the most efficient to produce. This determines the price. It’s why princess cut diamonds are more affordable, and round brilliants are not.

Unlike mined diamonds, lab created diamonds grow over a short period under lower heat.

Again, unlike mined diamonds, lab created CVD diamonds grow upwards into a cube.  Lab created HPHT diamonds grow into a cube-octahedron hybrid shape. This makes lab diamonds better suited to square shapes like the cushion, rather than elongated or flat shapes like the marquise or trillion. The rule of thumb? Inefficient = expensive.

A diagram showing the different crystal formations lab grown HPHP, CVD and mined diamonds grown in used to illustrate why diamonds test positive on a diamond tester

Like tree’s, diamonds have layers that indicate their growth pattern. With the right equipment, under extremely high magnification, you tell you whether a diamond originally grew into a cube, octahedron or cube-octahedron hybrid. Under super magnification in a lab, or using photoluminescence spectroscopy, it is possible for a trained gemologist to tell a lab diamonds apart from a mined diamond, by examining the growth pattern.

To Recap — Do Lab Diamonds Test Positive on a Diamond Tester?

Yes — but, there are three ways lab diamonds differ from mined diamonds.

1. Their type

Identifying a diamond as type Ia proves that is is mined. Identifying a diamond as type IIa does not prove that it is lab grown.

2. How the are grown

Under magnification, a diamonds growth pattern can indicate if it was mined, grown using CVD or grown using HPHT. In addition, certain diamonds have physical indicators that are relics of the growth process.

The presence of flux

Flux is only present in HPHT grown diamonds. Lab created diamonds rarely exhibit fluorescence.

The presence of fluorescence

Mined diamonds exhibit fluorescence about 30% of the time. Click here to learn more about diamond fluorescence and why it matters.

3. The shape of the rough

Lab diamonds grown into cubes. Mined diamonds grown into octahedrons.

Read to Get Started?

Check out our diamond search where you can view 360-degree images of more than 10,000 diamonds and don’t forget to zoom out (because size can be deceiving), or book an appointment at our New York salon to view certified lab-grown and natural diamonds in person. 

Not finding what you’re looking for? Email us with what you’re looking for at hello@frankdarling.com. We’ll curate a list of 5-7 exclusive stones that are just right for you.