Shopping for a diamond, you will quickly meet two terms that sound similar but mean very different things: lab-grown diamonds and simulated diamonds. Confusing the two can cost you thousands or leave you with a stone that is nothing like what you expected. Here is exactly what separates them.
A lab-grown diamond is a real diamond - identical carbon crystal, 10 on the Mohs hardness scale, graded on the four Cs. A simulated diamond (a "simulant") only looks like a diamond; cubic zirconia and moissanite are the common examples, and they differ in hardness, brilliance and price. Lab-grown is a diamond; a simulant is an imitation.
What is a lab-grown diamond?
A lab-grown diamond is pure crystallized carbon created in a laboratory using High Pressure High Temperature (HPHT) or Chemical Vapor Deposition (CVD). Chemically and optically it is indistinguishable from a mined diamond, and it can carry GIA or IGI certification on the same grading scales. If you are new to the category, our beginner guide to lab-grown diamonds is a good starting point.
What is a simulated diamond?
A simulated diamond imitates the appearance of a diamond without sharing its composition. The two most common are cubic zirconia (a synthetic form of zirconium dioxide) and moissanite (silicon carbide). They can look convincing at a glance, but they behave differently: cubic zirconia is softer and can cloud over time, while moissanite produces a more rainbow-like flash and is not a diamond at all. Neither is graded as a diamond.
The key differences
- Composition: lab-grown is carbon (a true diamond); simulants are different materials entirely
- Hardness: lab-grown scores 10 on the Mohs scale; cubic zirconia around 8, moissanite around 9.25
- Sparkle: lab-grown shows classic diamond brilliance; moissanite gives a stronger rainbow fire; cubic zirconia can look glassy
- Durability: lab-grown resists scratches and cloudiness for a lifetime; cubic zirconia may dull with wear
- Value and certification: only lab-grown diamonds are graded and certified as diamonds
Which is right for you?
If you want a genuine diamond that will last a lifetime and hold its clarity, choose lab-grown - especially for daily-wear pieces like engagement rings and everyday diamond earrings. Simulants can suit costume pieces or travel jewelry where a lower price outweighs longevity. For a full breakdown of lab-grown against mined stones, see lab-grown versus natural diamonds, or browse the lab-grown diamond collection.
Frequently asked questions
Is moissanite a lab-grown diamond? No. Moissanite is a diamond simulant made of silicon carbide. Some moissanite is lab-created, but it is never a diamond.
Will a simulant pass a diamond tester? Cubic zirconia will fail a standard diamond tester. A lab-grown diamond passes because it is a real diamond.
Do simulants hold value? Generally no. Simulants are inexpensive and are not valued or certified as diamonds, whereas lab-grown diamonds are graded gemstones.
