Moissanite vs Lab-Grown Diamond: Which Lab-Made Stone to Buy

Both stones are grown in a lab, which is why people put them side by side. That is where the similarity ends. A lab-grown diamond is diamond: same carbon crystal, same hardness, same light behavior as a diamond from a mine. The FTC confirmed in its 2018 Jewelry Guides update that a lab-grown diamond is a diamond, as long as its origin is clearly disclosed. Moissanite is silicon carbide, a different mineral that imitates diamond.

Choose moissanite when the lowest possible price for a big stone is the goal. Choose lab-grown diamond when you want the real material, the classic diamond look, and a stone graded on the same 4Cs a jeweler uses for any diamond. For engagement rings and anything you will wear every day for decades, we point people to lab diamond.

Lab-grown diamond starts as a thin diamond seed. In the CVD method, carbon from a gas settles onto the seed layer by layer. In the HPHT method, carbon is pressed and heated until it crystallizes, copying the conditions deep in the earth. Either way the result is diamond, and a gem lab can only tell it from a mined stone with specialized instruments.

Moissanite was first found in tiny amounts in a meteorite crater. Natural moissanite is far too rare for jewelry, so all gem moissanite is made in a lab from silicon and carbon. It has been sold as a diamond alternative since the late 1990s.

So the honest way to put it: lab diamond is a diamond with a lab origin. Moissanite is a lab gem that looks like diamond.

Lab diamond is a 10 on the Mohs scale. Moissanite is 9.25. That gap sounds small, but the Mohs scale is not even: diamond is several times harder than the next materials below it. For a ring that gets knocked around every day, that is the difference between facet edges that stay crisp for a lifetime and edges that may show tiny wear after many years.

Both are tough enough for daily wear. Neither is indestructible. Points on pear, marquise and heart shapes can chip on a hard hit, so they need a prong or V-tip at the point. Our house collection includes pointed shapes, such as the Heart Lab Diamond Ring 3.14 ct, 14K White Gold at $3,900; see the pear lab diamond rings too.

Put a 2 carat lab diamond next to a moissanite of the same millimeter size and you will notice three things:

1. Color play. The moissanite flashes more red, orange and violet, especially in sunlight. The lab diamond shows more crisp white light with some fire.
2. Color tone. A lab diamond graded E color is in the colorless range on the GIA scale. Moissanite has no color grade of its own, and larger stones can show a faint warm or gray tint next to a true colorless diamond.
3. Facet doubling. Under a 10x loupe, moissanite shows doubled facet edges because it splits light into two rays. Diamond does not.

If you want a stone nobody questions at any distance, lab diamond is the one. Our house lab rings are E color, VS1 clarity, which means colorless and eye-clean.

Moissanite is still cheaper, but the gap is the smallest it has ever been. Lab-grown diamond prices dropped hard after 2020 as production grew. Here is what E color, VS1 lab diamond rings actually cost in our showroom catalog:

Those prices include the 14K gold setting, and notice that price follows more than weight: shape, center size and design all move it, which is why the 4.62 ct round costs less than the 3.75 ct cushion. A moissanite ring of similar look will cost less, but you are now comparing a few hundred to a couple thousand dollars of difference, not the tens of thousands that separated moissanite from mined diamond a decade ago.

A basic thermal pen beeps "diamond" on both stones, because moissanite moves heat almost as well as diamond. A multi-tester adds an electrical conductivity check: moissanite conducts, most diamonds do not, so moissanite gets flagged.

There is one catch worth knowing. Some HPHT lab diamonds contain traces of boron, and boron lets a diamond conduct a little electricity. Tester makers warn that those stones can read "moissanite" on electrical testers. A jeweler then confirms with a loupe (no doubled facets means diamond) or with the stone's grading report. Lab diamonds are normally sold with an IGI or GIA report and often a laser inscription on the girdle that matches it; ask for the report number and check it on the lab's website. More in GIA and IGI certificates.

Diamond is sold by weight. Moissanite is lighter for its size, so it is sold by millimeters or by a "diamond equivalent weight" (DEW), meaning the weight a diamond of that size would have. If you compare a "2 carat DEW" moissanite with a 2 carat lab diamond, you are comparing the same face-up size, not the same weight.

The moissanite column is approximate, calculated from the density difference (about 3.22 for moissanite against 3.52 for diamond), so the same size weighs roughly 9% less. Cut proportions change real numbers a little. The lesson: compare millimeters, then compare price.

The FTC Jewelry Guides set the rules in the US. For lab-grown diamonds, the seller must make the origin clear with words like "lab-grown," "laboratory-created" or "[manufacturer]-created," placed close to the word diamond. The words "real," "genuine" and "natural" may not be used for a lab stone. For moissanite and other simulants, the seller may not call the stone a diamond at all.

What that means for you: a listing that says only "diamond" for a stone that is lab-grown breaks the rule, and a listing that says "moissanite diamond" is misleading. Our house rings name the origin in the title, for example "Round Lab Diamond Ring 1.5 ct, 14K White Gold," and list the center stone grade as E color, VS1.

Price on the day you buy is only part of the cost. Think about what each stone looks like after a decade on your hand.

• Lab diamond: the stone itself will look the same in ten years. What needs attention is the setting. Have prongs checked once a year, and keep the gold clean so light can enter the stone from the sides.
• Moissanite: the stone stays bright, with possible light wear on the sharpest edges if you are hard on rings. Same prong checks apply.
• Upgrading later: some people buy moissanite now and plan to swap in a diamond later. That works if the setting fits the new stone's exact size, which is another reason to compare by millimeters.

Neither stone is a financial asset. Lab diamond resale is low, moissanite resale lower still. Buy the one you will be happiest looking at every day.

• "Lab diamond is basically moissanite." No. One is diamond, one is silicon carbide. They share a birthplace, not a material.
• "Moissanite is harder to scratch than lab diamond." No. Lab diamond is a 10, moissanite a 9.25.
• "Lab diamond can't be graded." It can. IGI grades most of the lab diamonds on the market, and GIA issues its own report for lab-grown stones.

For iced necklaces, total carat weight is where lab diamond shines. Our Round Lab Diamond Necklace 18.48 ct, 14K Yellow Gold is $6,500, and the Round Lab Diamond Bracelet 7.49 ct, 10K White Gold is $2,200.

Go with moissanite if the budget is fixed, the stone is for fashion rather than a lifetime, and you like extra color flash.

Go with lab-grown diamond if you want real diamond, a 4Cs grade you can compare, and a stone that passes every look and every test. For most engagement rings, that is the answer.

Browse lab diamond engagement rings by shape: radiant, emerald and oval. The lab-grown diamonds guide covers how they are made, and moissanite vs diamond compares moissanite with natural stones.