Do Lab Grown Diamonds Pass a Diamond Tester?

Yes, lab grown diamonds pass standard diamond testers. They register as real diamonds because they are real diamonds: same carbon crystal structure, same thermal conductivity, same optical properties as any stone pulled from the earth. The only scenario where a result might look off involves HPHT-grown stones tested on certain electrical conductivity testers, and even then the stone is still a diamond. A tester confirms what a stone is made of, but cannot tell you where it came from.

How does a diamond tester actually work?

Most handheld testers sold at jewelry counters and online measure thermal conductivity: how fast a stone pulls heat away from a small metal probe. Diamond is one of the best heat conductors on earth, moving heat more than five times faster than copper or silver. When the probe touches a diamond, the temperature drop is so fast and steep that the tester registers “diamond” in about one to two seconds.

That speed is the same whether the diamond grew underground over billions of years or in a reactor over a few weeks. The physics does not care about origin.

The complication came in the early 2000s when moissanite arrived as a diamond simulant. Moissanite conducts heat almost as well as diamond, so thermal-only testers started flagging it as diamond by mistake. Manufacturers responded by adding a second measurement: electrical conductivity. Most diamonds conduct heat well but barely conduct electricity, while moissanite conducts both. A dual tester uses that difference to separate them.

Why do lab grown diamonds pass the thermal test without question?

Because the thermal properties of a lab grown diamond are identical to those of a mined diamond. Both are pure carbon in a cubic crystal lattice. The growth method (HPHT or CVD) changes the manufacturing environment, not the resulting atomic structure. When the probe touches the table of a lab grown stone, the heat dissipates at exactly the same rate it would from a natural diamond. The tester has no way to distinguish between them, and that is not a flaw in the tester. It is just physics.

CVD diamonds, which are grown by depositing carbon gas layer by layer, tend to be very close to Type IIa diamonds: high thermal conductivity, very low electrical conductivity. They pass both the thermal and electrical portions of a dual tester cleanly.

Is there any case where a lab grown diamond might get a confusing result?

Yes, and it is worth knowing about. HPHT-grown diamonds can sometimes contain trace amounts of boron, which gets incorporated into the crystal during the high-pressure growth process. Boron makes a diamond slightly electrically conductive. On a dual tester checking electrical conductivity to rule out moissanite, a boron-bearing HPHT stone may produce an inconclusive or “moissanite” reading, even though it is a genuine diamond.

This does not mean the stone is fake or inferior. It means the handheld tester ran into its own limitation. According to GIA research published in Gems & Gemology, roughly 70% of colorless HPHT lab grown diamonds contain some boron, which is why this comes up more often than many buyers expect.

Some HPHT stones also contain tiny metallic inclusions (iron or nickel from the growth catalyst) that can affect how a tester reads thermal conductivity near the surface. Again, the stone is still a diamond. The tester is just not designed to handle that particular variable.

The takeaway: if you test a lab grown diamond and get an odd result, the problem is almost certainly the tester’s electrical conductivity circuit, not the stone.

What can a diamond tester tell you, and what can it not?

A standard tester answers one question: is this stone a diamond? It cannot answer a second, separate question: is this diamond mined or lab grown?

That second question requires equipment that no handheld probe can replicate. Gemological labs like GIA and IGI use spectroscopy, UV fluorescence imaging, and tools like advanced diamond imaging technology to examine growth patterns and trace elements that are unique to each origin type. Those patterns are invisible to a thermal probe.

So if someone hands you a lab grown diamond and you run it through a tester, it will pass. That is correct. It is a diamond. But the tester will not print “lab grown” on its display, because it simply cannot make that determination.

What does IGI or GIA certification actually confirm that a tester cannot?

A diamond tester tells you what a stone is made of. A grading report from IGI or GIA tells you everything else.

IGI’s process includes advanced spectroscopy to confirm lab grown origin, identification of the growth method (HPHT or CVD), full 4Cs grading, and a laser inscription on the girdle that links that specific stone to that specific report. You can verify any IGI report number directly on IGI’s website in under a minute. GIA follows a similar process, laser-inscribing the girdle with the words “Laboratory-Grown” alongside the report number.

That inscription is the real test. It is permanent, visible under 10x magnification, and tied to a document you can cross-check against the lab’s own database. No handheld probe comes close to that level of documentation.

The certificate is the only document that closes the origin question entirely: not a formality, but the definitive answer.

Certification, Not a Tester, Is What Protects You

A diamond tester is a useful screening tool. It will correctly identify a lab grown diamond as a diamond every time a thermal probe is used, and in most cases with an electrical probe too. The one exception, certain HPHT stones on dual testers, is a limitation of the device, not evidence of anything wrong with the stone.

What a tester cannot do is confirm origin. For that, you need a grading report from a recognized lab. If you are shopping for a lab grown diamond engagement ring and want full confidence in what you are buying, the certification is the document that delivers it, and Dvik Jewels includes IGI or GIA documentation with every lab grown diamond for exactly that reason.

FAQs

1. Will a lab grown diamond pass a diamond tester at a jewelry store?

Yes. Lab grown diamonds are chemically and physically identical to mined diamonds, so any standard thermal conductivity tester will confirm them as diamonds. Most dual testers (thermal plus electrical) will also return a positive result, with the rare exception being certain HPHT stones that contain boron.

2. Can a diamond tester tell the difference between a lab grown diamond and a natural diamond?

No. Standard handheld testers measure thermal and electrical conductivity, and those properties are the same in lab grown and mined diamonds. Distinguishing origin requires spectroscopic analysis and UV fluorescence imaging, which only gemological labs like IGI and GIA can perform.

3. Why did my lab grown diamond test as moissanite on a dual tester?

This most often happens with HPHT-grown lab diamonds that contain trace boron, which makes the stone slightly electrically conductive. A dual tester interprets electrical conductivity as a sign of moissanite and flags the result. The stone is still a genuine diamond. Your IGI or GIA certificate confirms the actual identity.

4. Does the growth method (CVD vs. HPHT) affect how a diamond tests?

It can, on the electrical conductivity portion of a dual tester. CVD diamonds tend to pass both thermal and electrical tests cleanly. Some HPHT diamonds, due to boron content or metallic inclusions from the growth process, may produce an inconclusive reading on the electrical test. Thermal-only testers return a clean “diamond” result for both types.

5. Is IGI certification enough to prove a diamond is lab grown?

Yes. IGI uses spectroscopy and growth-pattern analysis to confirm origin, then laser-inscribes the diamond’s girdle with a report number and the “lab grown” designation. You can verify that report number on IGI’s website against the stone’s measurements and grades. That combination of physical inscription and online verification is the standard for confirming a diamond’s origin.