What Is Moissanite? And How It Compares to Diamond

Moissanite is silicon carbide, a crystal made of silicon and carbon that is rare in nature and almost always grown in a laboratory when it is used in jewelry. It was first found in meteorite debris, and it ranks just below diamond in hardness. Cut well, it is colorless to near-colorless and throws more colorful flashes of light than a diamond does. It looks a lot like a diamond to the eye, but it is a different material with different properties, which is why a jeweler can tell the two apart and why you should know which one you are buying.

Where moissanite comes from

The mineral is named for Henri Moissan, a French chemist who studied fragments from a meteorite crater in Arizona in the 1890s and eventually identified the sparkling crystals in them as silicon carbide. The mineral was later named in his honor. Natural moissanite is extraordinarily scarce on Earth. It has turned up in tiny grains in a few geological settings and in meteorites, but never in sizes or quantities that could supply a jewelry market.

The moissanite in rings, earrings and bracelets today is lab-created. Silicon carbide had been made for industrial use as an abrasive for a long time. In the 1990s, researchers learned to grow single crystals of gem quality, and GIA documented the first synthetic moissanite as a diamond simulant in the late 1990s. Because the material is made on purpose rather than mined, size and supply are not limited the way they are with natural gems.

So when a listing says "moissanite," assume it is lab-created. That is not a flaw. It is simply what the product is. It is also a different thing from a "lab-grown diamond," which is real diamond, chemically identical to a mined one. Our guide Lab Grown vs Natural Diamonds: What Changes covers that distinction in detail.

How moissanite compares with diamond

The table below sets out the properties that matter when you hold the stones side by side. Figures are the commonly cited gemological values, rounded.

Two lines in that table matter more than the others. The first is hardness. A stone at 9.25 on the Mohs scale resists scratches from almost everything a person meets in daily life, and it is far harder than cubic zirconia. Diamond is still harder, and diamond can scratch moissanite, but ordinary wear rarely tests that gap. The second is double refraction, which gets its own section below because it is the quickest way to separate moissanite from diamond.

Brilliance, fire and color

Brilliance is the white light a stone returns to your eye. Fire is the rainbow flashes of color. Moissanite has a higher refractive index and a higher dispersion than diamond, so it tends to return a lot of light and to split it into more spectral color. Many buyers love this. Others find that the rainbow flash looks busier and less "icy" than the crisp white and gray sparkle of a diamond, especially in daylight and under bright store lighting.

Neither is better in a universal sense. It is a matter of taste. A useful habit is to look at both in the same light, indoors and out, before deciding.

Color is the other thing to watch. Early moissanite often carried a faint yellow, green or gray tint, which was visible in some lighting and especially in larger stones. Modern production offers colorless and near-colorless grades. Sellers use their own descriptors, and moissanite is not graded on the same diamond color scale that GIA uses for diamonds. If you want to understand what that diamond scale means for comparison, see Diamond Color Chart: D to Z Explained. For clarity, moissanite is usually described as eye-clean, and some stones contain tiny needle-like inclusions, which is a growth feature of the crystal. Diamond Clarity Chart: What Each Grade Means explains the diamond vocabulary, though it does not apply neatly to moissanite.

How to tell moissanite from diamond and from CZ

Several quick checks help. None is a guarantee on its own, and a mounted stone in a bezel is harder to test.

• Look for doubled facet edges. Moissanite is doubly refractive. Light entering the stone splits into two rays, and under magnification the back facet edges appear doubled, as if the lines were drawn twice. GIA has described this as the easiest way to separate it from diamond, which is singly refractive. Looking through the crown at a slight angle with a loupe is the usual method.
• Know that a basic diamond tester can be fooled. Inexpensive thermal testers measure how well a stone conducts heat, and moissanite conducts heat much like diamond, so it can read as "diamond." Some newer testers are designed to detect moissanite, and a tester that checks electrical conductivity as well will separate them. Ask which type was used.
• Judge the weight. Moissanite is lighter than diamond at the same size, so a loose moissanite of the same millimeter size will weigh less than the diamond. This is also why moissanite is usually sold by millimeter dimensions rather than carat weight.
• Look at the sparkle pattern. Cubic zirconia is typically heavier, can look glassier and a little too colorful, and can show wear, cloudiness or surface scratches with time. It also has no doubling.
• Ask for documentation. A report or receipt from a recognized laboratory or reputable appraiser that names the material removes the guesswork. Our guide How to Spot a Fake Diamond walks through the testing options in more detail, and Jewelry Appraisal: What It Is and What It Costs explains what an appraiser actually checks.

If you are looking at a stone that someone is passing off as a diamond and you suspect moissanite, a professional gemologist can confirm it quickly, and it matters because the stones are valued very differently.

Durability and everyday wear

Moissanite is tough enough for daily wear in a ring. At 9.25 it is slightly harder than sapphire and ruby, which sit at 9. It handles heat well, holds up in normal cleaning, and does not need special treatment to keep its look. It is not chipping-proof. Any gem can chip if it takes a sharp blow on a vulnerable edge, particularly at a girdle that was cut very thin.

Three practical points:

1. Cleaning is simple. Warm water, a little mild dish soap and a soft brush are enough. Dry it and check that the prongs are not loose.
2. Oils and lotions dull it. Like diamond, moissanite attracts grease, so it may look a little flat until cleaned.
3. The metal needs care too. A durable stone in a worn setting can still fall out. Have a jeweler check prongs periodically.

Buying notes

Moissanite is generally much less expensive than a natural diamond of the same apparent size, and it is often compared with lab-grown diamonds for the same reason. That is a reason to buy it. It is not a reason to be careless about what you are paying for. A few buying habits help.

• Confirm that it is labeled moissanite. The listing, the paperwork and the seller's description should all say so, rather than "diamond-like," "brilliant stone" or similar vague wording.
• Check the cut. A cut moissanite should have even facets and a symmetrical outline. A poor cut wastes the stone's optical advantage.
• Check the setting metal and marks. A moissanite set in gold or platinum is a mix of a lab-created stone and a precious metal, so the metal's marks matter. Our guide How to Tell If Gold Is Real is a good starting point, and What Does 14K Actually Mean? explains the stamps.
• Think about resale. Moissanite does not carry the same long resale market that natural diamonds do, so treat it as something you buy to wear and enjoy. The price of a piece at resale will depend more on the metal, the maker and the setting than on the stone. See What Determines the Value of Fine Jewelry for how buyers think about this.
• Know the difference from an old mine-cut diamond. If a stone is in an antique setting, an estate jeweler should be able to tell you which it is. Our guide What Is Estate Jewelry? explains how that category works.

Seeing it live

Watching a piece sold live is one way to see a stone's behavior before you commit. Light moves, the seller can rotate the piece in front of the camera, and you can ask whether the stone is moissanite, lab-grown or natural before you bid. Sellers on ShopBidz who handle jewelry, such as NYC Watches & Diamonds in New York, NY and DeJesusTreasures in Wallingford, Connecticut, sell live, which means you can ask questions in the moment about the stone, the metal and any paperwork. Ask the same questions every time: what is the stone, how was that determined, what is the metal and how is it marked, and what is the return policy. Our The Live-Auction Glossary: Terms Every Bidder Should Know explains the terms you will hear.

Common mistakes

• Assuming sparkle means diamond. Moissanite and cubic zirconia both sparkle. Identification takes a test, not a glance.
• Trusting a basic diamond tester alone. Some testers read moissanite as diamond. Use a tester designed to separate them, or check for doubled facets under magnification.
• Comparing carat weight directly. Because moissanite is lighter, a stone sold by its millimeter size is not the same as a diamond of the same carat weight.
• Treating "lab-created" as "lab-grown diamond." Moissanite is a different mineral, not a type of diamond.
• Skipping paperwork. If a stone is described as a diamond, ask for a report that names the material. If it is moissanite, make sure the receipt says so.

Bottom line

Moissanite is lab-created silicon carbide that looks like diamond to the casual eye, ranks just below it in hardness, and shows more fire. It is durable enough for everyday jewelry and is a legitimate gem in its own right. It is also a different material, so it should be labeled and valued as one. A loupe will show doubled facet edges in most stones, and a professional can confirm the rest. Buy it because you like how it looks and wears, and make sure the description, the paperwork and the price all say moissanite.