Lab-Grown Diamonds vs. Moissanite: What Is the Real Difference?

When you are comparing lab-grown diamonds and moissanite, the question sounds simple - but the answer has real-world consequences for what you are buying. These two stones look similar in a jewelry case. Under a microscope or with an eye loupe, a trained gemologist can tell them apart. More importantly: they are fundamentally different materials, made of different atoms, with different crystal structures and different optical behaviors.

Here is the real difference - not the marketing version.

The Chemistry: What Are They Actually Made Of?

Lab-Grown Diamond

A lab-grown diamond is made of carbon - pure carbon atoms arranged in a tetrahedral lattice structure. This is the same structure found in every natural diamond mined from the Earth. The crystal system is cubic. The chemical formula is simply C.

This is why the Gemological Institute of America (GIA) and the International Gemological Institute (IGI) certify lab-grown diamonds using the same grading scales as mined diamonds. A lab-grown diamond is not "like" a diamond - it is a diamond.

Moissanite

Moissanite is silicon carbide - chemical formula SiC. It was first discovered in 1893 by French chemist Henri Moissan inside a meteorite crater in Arizona. Natural moissanite is extraordinarily rare. Modern moissanite sold in jewelry is entirely lab-created - grown in a controlled environment, not pulled from a meteor.

Silicon carbide is a semiconductor material. It is used in electronics, cutting tools, and industrial applications. In gem form, it was developed as a diamond alternative by Charles & Colvard in the 1990s. It is a real mineral - but it is not a diamond, and it never claims to be one.

Side-by-Side: Key Properties Compared

Property	Lab-Grown Diamond	Moissanite
Chemical composition	Pure carbon (C)	Silicon carbide (SiC)
Crystal structure	Cubic	Hexagonal
Mohs hardness	10 (hardest known mineral)	9.25
Refractive index	2.417–2.419	2.650–2.690
Brilliance (BRI)	2.42	2.65
Fire (dispersion)	0.044	0.104
Birefringence	None (singly refractive)	Yes (doubly refractive)
Independent certification	IGI, GIA	Manufacturer grading reports

The Visual Difference: Sparkle, Fire, and Color

How a Diamond Sparkles

Diamonds produce a mix of white light return (brilliance) and spectral color flashes (fire). Because diamonds are singly refractive, the light path through the stone is clean and predictable. The result is what most people think of as "diamond sparkle" - a balance of bright white flashes and sharp, crisp color play.

How Moissanite Sparkles

Moissanite has a higher refractive index and a higher dispersion value than diamond. That means it bends light more and splits it into more spectral color. The result is rainbow-like flashes that are visually distinct - some people love it, but it reads as different from the sparkle of a diamond to trained and untrained eyes alike. In large stones (over 1.5–2 carats), the difference is often noticeable without magnification.

Moissanite is also doubly refractive, meaning light splits into two rays inside the stone. Through a loupe or microscope, this creates a "doubling" effect where facet edges appear duplicated.

Color Differences

Modern moissanite is available in colorless grades (equivalent to approximately D–E–F on the diamond color scale). However, in larger sizes and in certain lighting conditions, some moissanite stones can show a faint yellow or green tint that is not present in a comparable colorless lab-grown diamond.

Lab-grown diamonds from EX3 are graded using the standard IGI color scale - D through Z - with the same precision used for mined diamonds. The color you see in the certificate is the color you get.

Hardness: Does It Matter in Everyday Wear?

The Mohs hardness of diamond at 10 makes it the hardest naturally occurring substance known. Moissanite at 9.25 is extremely durable - the second hardest gemstone used in jewelry (after diamond) - and is far more scratch-resistant than sapphires, rubies, or any other popular stone.

In practical terms: both diamond and moissanite are excellent for everyday wear in engagement rings. You are not going to scratch either stone on normal surfaces. The hardness difference matters more in industrial applications than in jewelry.

Price: What Are You Actually Paying For?

Moissanite is significantly less expensive than lab-grown diamonds. A 1-carat colorless moissanite typically retails for $300–$600. A 1-carat lab-grown diamond in a comparable quality ranges from $700–$1,500+, depending on cut, color, and clarity.

The price difference exists because they are different materials. You are not paying a diamond "premium" for a lab-grown diamond - you are paying for a diamond. The carbon atom, the tetrahedral lattice, the IGI certificate, the 10 on the Mohs scale - those are what the price reflects.

If your primary goal is the largest stone at the lowest cost, moissanite is a legitimate choice. If you want a diamond - real diamond, with an independent grading certificate, at a fraction of mined diamond prices - that is what a lab-grown diamond gives you.

Certification: How Do You Know What You Have?

Lab-grown diamonds larger than a certain carat threshold receive independent grading certificates from the IGI or GIA. These documents state the exact cut, color, clarity, and carat weight of the stone, verified by a laboratory that has no financial interest in the outcome.

Moissanite does not receive IGI or GIA diamond grading reports. Manufacturers issue their own quality reports, but these are not independently verified by a third-party gem lab using diamond grading standards.

When you buy an EX3 Diamond lab-grown diamond, you receive an IGI certificate - an independent document confirming exactly what the stone is and what grade it received.

What About the "Diamond vs. Moissanite" Tester?

Traditional diamond testers use thermal conductivity to distinguish diamonds from cubic zirconia and other simulants. Because moissanite has high thermal conductivity similar to diamond, many basic diamond testers will register moissanite as a diamond. This is a flaw in those older testers, not a feature of moissanite.

Modern multi-tester devices that combine thermal and electrical conductivity testing can distinguish between diamond and moissanite. Any reputable jeweler will have one. Any lab-grown diamond from EX3 will pass both tests and come with an IGI certificate confirming it as a diamond.

Which Should You Choose?

There is no wrong answer - it depends entirely on what you are looking for.

Choose moissanite if:

• Budget is the primary factor and you want maximum carat size per dollar
• You love the distinctive high-fire, rainbow sparkle of silicon carbide
• You do not place significance on independent certification or diamond status

Choose a lab-grown diamond if:

• You want an actual diamond - certified by IGI, composed of carbon, graded on the same scale as mined diamonds
• You care about the stone holding up under expert gemological examination
• You want the precision that comes with a cut, color, and clarity certificate
• You want conflict-free, traceable provenance with full documentation

EX3 Diamond makes lab-grown diamonds for people who want the real thing without the mined diamond price tag. Every stone is grown in our OB1X CVD chamber, cut to ideal standards in Illinois, and certified by IGI before it becomes an engagement ring or a loose diamond in your hands.

Frequently Asked Questions

Is moissanite a diamond?

No. Moissanite is silicon carbide (SiC). Diamond is pure carbon (C). They are distinct minerals with different chemical compositions, crystal structures, and optical properties. Moissanite is a diamond alternative - not a diamond.

Can you tell the difference between a diamond and moissanite?

An experienced jeweler can tell them apart using a loupe, a multi-tester, or by observing the distinctive double refraction of moissanite. In large stones (1.5+ carats), the higher fire and rainbow flashes of moissanite may be visible to an untrained eye under certain lighting.

Does moissanite hold its value like a diamond?

Neither lab-grown diamonds nor moissanite are investment-grade assets in the same category as rare mined diamonds. Lab-grown diamond prices have decreased significantly. Moissanite resale value is typically minimal. Neither should be purchased as a financial investment.

Is lab-grown diamond better than moissanite?

They serve different purposes. If you want a diamond - chemically, optically, and by IGI certification - then a lab-grown diamond is the only choice. If you want a lower-cost, larger-appearance alternative that is not a diamond, moissanite is a legitimate option.

Are EX3 lab-grown diamonds IGI certified?

Yes. Larger EX3 lab-grown diamonds receive IGI certification - an independent grading report documenting cut, color, clarity, and carat weight. This is the same IGI that grades mined diamonds.

Does moissanite pass a diamond test?

Older thermal conductivity diamond testers may register moissanite as a diamond because of similar thermal properties. Modern multi-testers that also measure electrical conductivity can accurately distinguish the two.

The Bottom Line

Lab-grown diamonds and moissanite are not two versions of the same thing at different price points. They are two different materials. One is a diamond. The other is silicon carbide designed to resemble a diamond.

If you want a diamond - real, certified, conflict-free, and grown above ground rather than below it - explore EX3 Diamond lab-grown diamond collection or build your ideal engagement ring starting today.

EX3 Diamond: Responsible. Traceable. Scintillating.