Moissanite vs diamond
Moissanite and diamond look alike at a glance but they are different gems. Diamond is harder (10 vs 9.25 on the Mohs scale). Moissanite has more than twice the fire (dispersion 0.104 vs 0.044), so it throws more rainbow flashes. Moissanite is about 10% lighter at the same size and costs a small fraction of the price. With a loupe, a jeweler can see doubled facet edges in moissanite.
Side by side
| Moissanite | Diamond | |
|---|---|---|
| What it is | Silicon carbide, lab-created | Carbon, mined or lab-grown |
| Hardness (Mohs) | 9.25 | 10 |
| Refractive index | 2.65 to 2.69 | 2.42 |
| Dispersion (fire) | 0.104 | 0.044 |
| Optics | Doubly refractive | Singly refractive |
| Weight at the same size | About 10% lighter | Reference |
| Heat in air | Stable to about 1,700°C | Starts to burn near 850°C |
Sparkle: more color
Moissanite bends light more than a diamond and splits it into more color. In sunlight or under spotlights it shows bigger rainbow flashes, most visibly in stones of 2 carats and up. Some people love that extra color, others prefer the cooler white sparkle of a diamond. Neither is better; it is a matter of taste.
Hardness: close, but not equal
Diamond is the hardest natural material. Moissanite, at 9.25, is the next hardest gem used in jewelry and is harder than sapphire and ruby. For everyday wear both resist scratches from keys, knives and files. Both can chip from a hard knock against a sharp edge.
Weight and size
Moissanite is lighter than diamond: its specific gravity is about 3.22, diamond's is 3.52. So a moissanite of the same diameter weighs about 10% less. That is why moissanite is usually sold by size, with the carat given as diamond equivalent weight. Details on our guide to carat and size.
How to tell them apart
- Loupe: look through a side facet at 10x. Moissanite shows doubled facet edges; diamond does not.
- Tester: a thermal-only diamond tester can read moissanite as diamond. A multi-tester that also checks electrical conductivity identifies moissanite.
- Lab: a gem lab confirms it in minutes.
Which one should you choose?
Choose diamond if hardness 10, the word diamond and resale matter to you. Choose moissanite if you want a large, bright stone with lots of fire for everyday wear at a small part of the price, and you are happy to call it what it is.
Questions
Does moissanite look like a diamond?
At a normal viewing distance most people cannot tell. Up close moissanite shows more rainbow color, and with a loupe a jeweler sees doubled facet edges.
Is moissanite as hard as a diamond?
Almost. Moissanite is 9.25 on the Mohs scale; diamond is 10. Steel tools cannot scratch either one.
Does moissanite get cloudy?
No. Moissanite does not cloud or change color over time. Like any gem, it looks dull when lotion or soap builds up on it; a wash with warm soapy water brings it back.
Is moissanite cheaper than diamond?
Yes, by a lot. A moissanite of the same size costs a small fraction of a mined or lab-grown diamond.
More guides
- What is moissanite?
- Moissanite vs lab-grown diamond
- Moissanite carat and size
- What a GRA certificate means
- Will moissanite pass a diamond tester?
- Moissanite and silver care
By the moissaniteit team, Olivia Star Jewelry LLC, Florida. Updated 2026-10-11.