Columbia ISA
Diamonds – How to tell if a diamond is real
Columbia ISA home – ›

SEARCH *** Columbia ISA Audio/Video

DIAMONDS Your Guide to Buying
How to tell if a diamond is real

Quick Check: How to Check if a Mounted Diamond is a Real Diamond

If you have a diamond that is already placed in an engagement ring, this is a good indicator of whether it is fake or real.

To determine real vs. fake diamonds, first carefully examine the type of setting and mount that is used. Since real diamonds (whether mined or lab diamonds) tend to have a larger price tag, you will not find them set in cheap metals. A real diamond will typically only be set in metals such as white gold, yellow gold, rose gold, or platinum.

In order to tell what type of setting it is, look inside the rings center for markings. For example, if you see the notes 10KT, 14KT or 18KT, those refer to the type of gold that is used. If you see the letters PT or Plat, those refer to the metal platinum. Also, if you see any numbers such as 585, 770, 900, or 950, those could indicate gold or platinum too. If you do not see any of the above markings, but you see the letters C.Z. that means the gemstone is a cubic zirconia (a fake diamond).

How to Tell if a Diamond is Real

Real diamonds are mined from the earth, cut by a professional craftsman and sold by a known retailer, usually with a diamond certificate from a known gemological authority.

Fakes are usually cubic zirconium (CZ) or moissanite (silicon carbide), or worse, quartz or glass. Many known retailers sell jewelry with cubic zirconium instead of real diamond and this is fine, as long as the item is not passed off as real diamond.

Remember, you are the only one who can determine true intent of the giving, diamond or not, it is the intent that counts.

While some must have a real diamond, others are satisfied with looks alone. Some diamond alternatives can be very appealing.

The best option is to have the diamond appraised by a jeweler you trust, who can test the diamond without damaging it, but this will cost you. The following are some things you can do to check for fakes but remember these are only checks, not foolproof methods. One or more may eliminate a fake.

  1. Ask for a diamond certificate. When buying diamonds, a diamond certificate is the best way to make sure you are getting the real thing. Make sure it is from an impartial diamond grading authority (e.g. GIA, AGSL, EGL, PGGL) or an independent appraiser who is affiliated with a professional organization (like the American Society of Appraisers). The certificate should describe the diamond and say what the cut, color, clarity and carat weight are. Any reputable retailer will have the diamond certificate for your diamond before you purchase it so you can rest assured it is real. In addition, the retailer should allow you to see, either with a microscope or loupe, the diamond's described qualities on the certificate so you can verify the description.

    How to read a diamond certificate the Gemological Institute of America is the world’s foremost authority on diamonds. Contact GIA 800-421-7250 AGS Laboratories is among the best known and well respected diamond grading laboratories in the world. EGL USA is one of the world's premier independent gemological laboratories. PRECISION GEM GRADING LABORATORY

  2. Look through it. Diamonds have a high "refractive index" (meaning they sharply bend the light that passes through them). Glass and quartz have a lower refractive index, meaning they sparkle less because they bend light less, even when they've been cut nicely.

    • If the diamond is not mounted, turn it upside down and place it on a piece of newspaper. If you can read the print through the stone or even see distorted black smudges, then it probably isn't a diamond. (Unless the cut is disproportionate, in that case print can be seen through a real diamond.)
    • If the stone shows any sign of double refraction, it may be Moissanite (silicon carbide), a gemstone that is so similar to a diamond that even jewelers can have a hard time telling them apart. **look at the facet junctions from the top side of the stone, the 'star' facets' if you see what looks like double vision then that is the doubling effect.
    • If the diamond is mounted, you should not be able to see the bottom of a diamond looking directly from the top.
    • Draw a small dot with a pen on a piece of white paper. Place your unmounted diamond over the center of the dot. Look directly down on it and if your stone is not a diamond, you will see a circular reflection in the stone.

  3. Observe the reflections. A real diamond's reflections usually manifest in various shades of clear/gray. If you see rainbow reflections, you're either dealing with a low-quality diamond or a fake. This is not looking at the diamond, but reflected light thru the stone on a surface like a white sheet of paper.

  4. Take the bottom view: Under a microscope hold the stone table(top facet) down. If you see an orange flash only to the facets as you rock the stone, it is fake.

  5. Buy a Diamond Tester. These are readily available and can quickly indicate if it is a true diamond or simulant.

  6. Weigh the stone. Diamonds are weighed in carats. 1 carat equals 200 milligrams. Cubic zirconia weighs approximately 55% more than diamonds for the same shape and size. Use a carat or gram scale to compare the stone in question to a real diamond. Scales used are usually electronic (or a triple beam balance scale) capable of measuring to the hundreth of a carat. Make sure the scale has been calibrated properly.

  7. Check the setting and mount. A real diamond is not likely to be set in a cheap metal. Stamps inside the setting indicating real gold or platinum (10K, 14K, 18K, 585, 750, 900, 950, PT, Plat) are a good sign, while a "C.Z." stamp will give away that the center stone is not a real diamond.

  8. Put the stone under a UV light. Many (but not all) diamonds will exhibit blue fluorescence under an ultra violet or black light, so the presence of a medium to strong blue confirms that it is real. The absence of blue, however, does not mean it is fake; it could simply be a better quality diamond. If you see a very slight green, yellow, or gray fluorescence under ultraviolet light, it may be Moissanite.

  9. Test it with a heat probe. Real stones disperse heat quickly and they won't heat up with the probe. This takes about 30 seconds and is often done free of charge. It also doesn't hurt the stone the way some other ways of testing will.

  10. Have the diamond x-rayed. Real diamonds do not show up on an x-ray, glass, cubic zirconium and crystals all have slightly radiopaque quailities, diamonds are radiolucent.

  11. Use a jeweler's loupe to inspect the diamond. Mined diamonds usually have small imperfections or inclusions that can be seen this way. Cubic zirconium does not have these imperfections. For that matter, lab-grown diamonds (which should pass all of the other tests) usually don't have imperfections either.

  12. Put the unset diamond in some water. If it sinks it could be real but if it floats, it is fake.

  13. Hold the stone between your fingers and place in your mouth and exhale on it. If the stone stays "foggy" for 2-4 seconds, then it is not real. Real diamonds will have cleared by the time you look at them.
    (Be warned though - some jewellers cap cubic zirconium (CZ) bases with real diamond which will clear.)

  • If you take the stone for an independent appraisal, expect to pay between $45 and $85 in the USA, and make sure the stone never leaves your sight - because they could change or replace your diamond with a fake one of the same size.

  • Diamonds scratch glass, but so do many imitation stones.
  • Not a lot of fake diamonds can scratch sandpaper.
  • Get your stone registered. Once you know for sure that your diamond is real, whether through independent appraisal or grading lab, take your stone to a lab that can register and fingerprint your diamond. This will ensure you that you have your real stone, and no one will be able to switch it out without you knowing.

  • Don't be overly concerned if you cannot tell if the stone is a real diamond. Even the experts can be fooled sometimes.

  • There is no way to be 100% sure that a diamond is real unless there is a diamond certificate. If you buy a pawned item, something off a table at a market, or an item off of a marginal website, you are taking a big risk and chances are these items are not diamond.

Man-made Diamonds

  • Today, diamonds can be "grown" in a laboratory but they are still real. They cost a fraction of what a natural mined diamond costs, but they are (for the most part) chemically the same as natural diamonds. Telling the difference between a natural diamond and a synthetic diamond is best determined by a professional.

Diamonds Buying Guide
Diamond Rings
What is moissanite?
How to read a diamond certificate
Gold coins, jewelry
American Gold Eagle
Canadian Gold Maple Leaf
Gold Krugerrand
o Car Insurance - know before you buy
What is Cubic zirconia (CZ) and Moissanite?

Cubic zirconia is a synthetic gemstone that very closely resembles diamonds. Because of its startling diamond-like appearance and inexpensive price tag, cubic zirconia is a highly popular gemstone used most frequently in jewelry such as rings, earrings, bracelets and pendants. Although cubic zirconia is synthetic, it is inspired by its natural counterpart, zirconium oxide (ZrO2), first discovered in 1892 but too rare to be commercially profitable. Through a series of experiments, zirconium oxide and yttrium oxide were eventually melted together at temperatures reaching 4,982ºF (2,750ºC) to grow cubic zirconia crystals in the laboratory.

Cubic zirconia is crystalline, flawless, and clear enough to rate a "D" on the diamond scale for color. Though usually colorless, it can also be made in nearly any color, including soft yellow, characteristic of some diamonds. Cubic zirconia sparkles brighter than crystal and is harder than most gems, making it very durable. It also weighs about 65% more than diamond.

Testing the hardness of a stone - The Mohs scale

Cubic zirconia is softer than moissanite. Diamonds test as a 10 on the Mohs scale, moissanite is around a 9, almost as hard as diamond while Cubic zirconia is around 8.25. Moissanite is said to have more brilliance than cubic zirconia and is more expensive. CZ is made by melting zirconium oxide with another metal oxide. Moissanite, however, is a silicon carbide. They do both exist in natural states but are hard to find.

Moissanite was first discovered in 1893 by a French scientist named Henri Moissan. Moissanite was introduced to the jewelry market in 1998. Heating moissanite gradually will cause it to change color starting at around 150 degrees Fahrenheit. This color change can be diagnostic for distinguishing diamond from moissanite. Moissanite gemstones are sometimes marketed under the trademark Berzelian.