Metal that lasts
Moissanite vs Diamond: Fire, Hardness, and the $200 Reality
Moissanite is silicon carbide, 9.25 Mohs, more rainbow than a diamond, and a 6.5 mm round is $80–$250. It is not a fake diamond. It is a different stone with a different invoice.
Updated 27 Aug 2026 · 7 min read · moissanite vs diamond
Not diamond, not CZ, not a trick
Cubic zirconia is ~8 Mohs and clouds. Moissanite is 9.25 and does not cloud from wear. Diamond is 10. You can wear moissanite next to keys; you should not treat it as indestructible. A 6.5 mm (1 ct diamond-look) premium colorless moissanite is commonly $80–$250. The same size in lab diamond is $400–$900. That gap is the whole product.
Color grades on moissanite (colorless vs near-colorless) are a vendor language, not GIA. In sunlight a 8 mm moissanite will throw more rainbow than a diamond of the same millimetre. Some people love that. Some people find it loud on a 9 mm oval. Size is how moissanite “gets caught,” not the 6 mm everyday round.
The tests, the setting, the tennis bracelet
Look through the table with a 10× loupe. Doubled facet junctions mean moissanite. A single set of junctions plus a “LG” inscription is lab diamond. Set moissanite in 14k or platinum the same way you would set a diamond; the $25 rhodium-plated brass head is how a good stone looks cheap. For a line bracelet, 2–2.5 mm moissanite at $250–$600 for 16–18 cm is the version that can survive a desk, unlike a $40 CZ tennis that goes milky.
| Moissanite | Lab diamond | CZ | |
|---|---|---|---|
| Chemistry | SiC | Carbon | ZrO2 |
| Mohs | 9.25 | 10 | ~8 |
| 6.5 mm round | $80–$250 | $400–$900 | $5–$20 |
| Fire | Higher, rainbow | White + some fire | Glassy, then dull |
| 10-year daily | Holds | Holds | Clouds, scratches |
Who should still buy diamond
Anyone who cares about the secondary market, the word on the report, or a family that will police the difference at dinner. Anyone who wants a 5 mm stone that stays optically calm. Moissanite is the practical 7–8 mm upgrade. Diamond — lab or mined — is the quieter 5–6.5 mm classic. Mixing a moissanite center with mined melee is fine if you disclose it to the next jeweler.
Questions, answered
- Will moissanite pass a diamond tester?
- A cheap thermal tester may say yes. A dual thermal/electrical tester says moissanite. Jewelers own the second one.
- Does moissanite get cloudy?
- Grease on the pavilion makes any stone look dead. Wash it. Permanent clouding is a CZ story, or a damaged coating on a cheap coated stone — do not buy coated moissanite.
- Can I put moissanite in an heirloom setting?
- Yes, if the head fits the girdle. A 6.5 mm round is a 6.5 mm round. Tell the jeweler what it is so they pick the right tester and the right prong pressure.
