One is a diamond grown in a lab; the other is a different gemstone altogether. Here's how they compare on hardness, sparkle, labelling and price.
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The short answer
A lab-grown diamond is a diamond: carbon, with essentially the same physical, chemical and optical properties as a mined one. Moissanite is a different gemstone, silicon carbide, used as a diamond alternative.[1][2] Neither is "better". They're different materials at very different prices.
Side by side
| Property | Moissanite | Diamond (lab-grown or mined) |
|---|---|---|
| Material | Silicon carbide | Carbon |
| Mohs hardness | 9.25 | 10 |
| Refractive index | 2.648–2.691 | 2.417 |
| Dispersion ("fire") | 0.104 | 0.044 |
| Refraction | Double: facet edges can look doubled | Single |
Figures from GIA's Gems & Gemology and the International Gem Society's comparison chart.[2][3]
In practice, moissanite's higher dispersion shows as stronger rainbow flashes, and its double refraction is one way gemologists tell it apart from diamond. GIA notes that thermal diamond testers of the time reacted to synthetic moissanite as if it were diamond, which is why a proper lab report matters.[2]
How each must be labelled
- Lab-grown diamond: "laboratory-grown", "laboratory-created" or "[manufacturer]-created" must sit immediately before "diamond", equally prominent.[1][4]
- Moissanite: it isn't a diamond, so it can't be called one. Calling a stone "faux" isn't an adequate disclosure under the Guides.[1]
Paperwork
Lab-grown diamonds are commonly sold with a report from IGI or GIA (see our IGI vs GIA guide). Moissanite is often sold with a GRA certificate for the main stone; that's a supplier-side card, not a diamond grading report.[5]
What they cost
- Lab-grown diamond engagement rings averaged $4,300 for US couples married in 2025, against $7,000 for natural, according to The Knot's 2026 Real Weddings Study.[6]
- A 5 ct lab-grown tennis bracelet in 14K gold was listed at $4,150 at Brilliant Earth, and from $4,820 (or $2,892 on sale) to $6,210 at Blue Nile, on 12 November 2026 (see our bracelet guide).
- A sterling-silver moissanite tennis bracelet from one US seller, MYNSU, listed at $214.99 on 12 November 2026.[5] No authority publishes a moissanite price index, so compare listings.
Which to choose
Choose lab-grown diamond if you want a diamond, with a recognised grading report, at a lower price than mined. Choose moissanite if you want maximum sparkle per dollar and are happy with a different stone. Either way, buy from a seller that names the stone plainly on the product page.
- Brilliant Earth (lab-grown diamonds and moissanite)Retailer link
- Clean Origin (lab-grown diamonds)Retailer link
Sources
- eCFR, 16 CFR Part 23 (FTC Jewelry Guides). https://www.ecfr.gov/current/title-16/chapter-I/subchapter-B/part-23
- GIA Gems & Gemology, Synthetic Moissanite: A New Diamond Substitute (Winter 1997). https://www.gia.edu/gems-gemology/winter-1997-synthetic-moissanite-nassau
- International Gem Society, Properties of Diamond Simulants. https://www.gemsociety.org/article/diamond-and-simulant-comparison-chart/
- Plumb Club, Understanding the FTC Guidelines. https://plumbclub.com/understanding-the-ftc-guidelines-guide/
- MYNSU, Brezza Moissanite Tennis Bracelet product page. https://mynsujewelry.com/products/brezza-moissanite-tennis-bracelet-in-sterling-silver
- The Knot Worldwide, 2026 Real Weddings Study press release. https://www.theknotww.com/press-releases/the-knot-worldwide-unveils-2026-real-weddings-study
Sources opened on or before 12 November 2026.