What Is Moissanite? Material, Size and Testing
Moissanite is silicon carbide, a gem material with its own optical and physical properties. The moissanite commonly used in jewelry is lab-created. Diamond is carbon, so moissanite is a different gemstone from both natural and laboratory-grown diamond.
Is moissanite a lab-grown diamond?
No. Being grown in a laboratory does not make two materials the same. Lab-created moissanite is silicon carbide; a lab-grown diamond has diamond's carbon structure. Clear, faceted stones may look similar in a photograph, but appearance alone does not establish the material.
What gives moissanite its appearance?
Moissanite can show strong rainbow flashes as light passes through its facets. The visible effect also depends on cut, stone size, lighting and the viewing angle. A close-up photograph taken under bright lighting will look different from the same piece in soft daylight.
Moissanite is resistant to scratching, but the finished jewelry still needs care. Hardness does not mean that a gemstone, prong, silver base or plated surface cannot be damaged.
Can a diamond tester identify moissanite?
A thermal diamond tester responds to heat conduction. Moissanite can produce a diamond-like response on some thermal testers. A thermal result alone cannot distinguish moissanite from diamond.
Identification requires methods and interpretation appropriate to the stone. A jeweler or gemological laboratory can select suitable testing. A photograph of a probe, an indicator light or a beep is not a complete material identification.
Why do millimeters, carats and DEW differ?
- Millimeters (mm)
- Physical dimensions: diameter for a round stone, or length and width for an elongated shape.
- Carat (ct)
- A unit of weight. Stones of equal weight can have different face-up sizes because of their shape and cutting proportions.
- Diamond equivalent weight (DEW)
- A size comparison with diamond, rather than the moissanite's actual carat weight.
Moissanite and diamond do not have the same density, so equal dimensions do not mean equal actual weight. Read the millimeter measurements alongside the product's carat description. See the ring-size and stone-size guide for a practical on-hand comparison.
What else should I compare?
Look at the stone's shape, stated color, clarity information and cut details. Shape is the outline viewed from above. Facet arrangement, proportions and finish influence light return. Clarity describes internal and surface characteristics.
Descriptions such as D color, VVS or Excellent should be read in the context of the product information and any accompanying report. The terms are not interchangeable with the gem's material identity.
For everyday wear, the metal and finish matter too. Our S925 silver, plated finishes and care guide explains the silver base, the two color-dependent finish sequences and gentle cleaning.