Is Your Diamond Real? How to Spot the Difference Between Real and Fake Diamonds
Diamonds are one of the most sought-after gemstones in the world. There’s a market full of lookalikes, synthetic diamonds, and outright fakes, which can make it difficult to tell if what you have is the real deal. Maybe you’ve inherited a mysterious piece of jewelry, a generational engagement ring, a vintage bracelet, earrings (samples pieces pictured below), or you are simply curious about a recent purchase and you’d like to know more.
Here’s a guide to help you tell the difference between diamond simulants and diamond substitutes, at-home tests and how they work, and professional diamond testing methods.
Simulants vs. Substitutes: Know the Difference
Diamond simulants are materials that look like diamonds but have different chemical compositions. Simulants are made to look like diamonds, but they are not chemically or physically the same.
Cubic zirconia is 8.0-8.5 on the MOHS scale, doesn’t sparkle as much, and will be lower priced.
Moissanite which looks close to a diamond, is a 9.25 on the MOHs scale, has a more fiery, rainbow like appearance, and will be moderate in price.
White sapphire has a dull sparkle, is 9.0 on the MOHS scale, is less brilliant and less expensive.
Glass is an obvious fake with a weak sparkle and very low price.
Diamond substitutes are stones (sometimes real diamonds) that are used in place of natural diamonds for cost, ethical, or aesthetic reasons. A lab-created diamond is a real diamond but will cost less because it is man-made. Below are a lab-grown diamond engagement ring and diamond earrings.
Moissanite and white topaz (shown below) are not real diamonds but look similar to a diamond.
At-Home Diamond Tests (Easy But Not Foolproof)
While no home test is 100% reliable, combining several simple tests can give you a good idea of whether your stone deserves professional inspection.
Fog Test
Breathe on the diamond like you would a mirror. A real diamond will clear up instantly due to high thermal conductivity. A fake diamond will stay foggy for a few seconds.
Dot Test
This is done by drawing a small dot on white piece of paper, placing the flat side of the stone over the dot. With a real diamond you shouldn't see the dot clearly due to high refractivity. With a fake stone, you will see the dot or a reflection of it.
Cold Water Test
The water test is done by dropping the stone into a glass of water. A real diamond will sink quickly and remain unaffected in cold water. A fake diamond may sink slowly or react to the temperature.
UV (black light) test
This test is done by shining a UV light on the diamond in the dark. A real diamond may fluoresce blue (but not all do) while a fake stone like cubic zirconia may glow yellow or not at all. Moissanite can glow green or white.
Loupe Test
A loupe test (10x magnification) is done by using a jeweler’s loupe to inspect for flaws. A loupe is more powerful than a magnifying glass. A real diamond often shows small inclusions or imperfections. Fakes are often flawless or show bubbles like glass or cubic zirconia.
Scratch test
A scratch test (not recommended if the stone is in a setting) will show that a real diamond can scratch glass or metal. This test could damage a fake stone or the setting so caution should be used if trying this test.
Sparkle Test
A sparkle test is an observation-based test to check a diamond's sparkle. In this test the stone is moved under light while you look for bright flashes of white light (brilliance), colorful rainbow flashes (fire), and lively sharp reflections that change as the stones move. A real diamond typically shows intense white sparkle, well-balanced flashes of color and has a high contrast between light and dark areas.
At-Home Test Problems
Using at-home tests to spot the difference between real and fake diamonds can be helpful-but it comes with several important limitations and risks. Below are some of the risks.
False Positives or Negatives
Moissanite can pass some diamond testers due to similar thermal conductivity. Some real diamonds (especially low-quality or treated ones) may behave oddly under UV or fog tests. Results may be misleading.
Lack of Precision
Home tests can’t tell the difference between natural diamonds vs. lab-grown diamonds, or high-quality fakes and genuine diamonds. Home tests cannot tell the difference between cubic zirconia, moissanite, white sapphire, or glass). You will not get clarity, color, or carat information from a home test either.
Risk of Damage
There is a risk of danger from scratch tests or harsh handling that can scratch or chip a fake stone, damage a setting or mount, and diminishing the resale value of the piece.
Inability to Detect Treatments
Diamonds that have been fracture-filled, HPHT-treated, or coated can behave differently. These treatments don't show up in basic home tests but can affect the diamond’s value and durability. This necklace contains an irradiated blue diamond, and a fracture filled ruby and diamond ring.
No Professional or Market Value Validation
Even if a stone passes a home test, you can’t sell or insure it based on that alone. Jewelers, appraisers, or buyers will require a professional lab certification like GIA or IGI.
User Error
It is not uncommon for an untrained person to misinterpret signs like sparkle or fluorescence. Inconsistent test conditions (lighting or breath temperature) may negatively impact the testing. Subjective evaluation can lead to incorrect assumptions.
Home tests are good for a quick informal check and can help rule out obvious fakes like glass or cubic zirconia. Generally home tests use a diamond that is in a setting, but using a loose diamond is more effective. Home tests are not reliable for final decisions, especially for buying, selling, or insuring diamonds.
Professional Diamond Testing (Accurate & Reliable)
When you want a definitive answer for your diamond jewelry, gemologists use advanced tools and techniques that offer precise identification on whether a diamond is real.
Labs will use a combination of tests to determine if a diamond is real because no single test can reliably and accurately identify all types of diamonds, especially when distinguishing between natural diamonds, synthetic diamonds, diamond simulants, and treated or enhanced diamonds. A multi-test approach is essential for true authenticity.
Thermal Conductivity Testers
Conductivity tests measure how quickly heat disperses through the stone. When using a heat test, heat will disperse rapidly with a real diamond. However moissanite may pass as a diamond.
Electrical Conductivity Tests
Conductivity tests measure how well electricity flows through the stone. Moissanite will conduct electricity, but diamonds do not. This is a good test for differentiating between diamonds and moissanite.
Dual-Mode Testers
Using a combination of both thermal and electrical testing gives a more accurate assessment.
Magnification with a Jeweler’s Loupe or Microscope.
Professionals will look for inclusion or blemishes in diamond. They can also check for laser inscriptions on the girdle which is common in certified diamonds. A jeweler's loupe used by a professional can be used to check for facet sharpness, polish quality, and symmetry. It can also spot double refraction in moissanite.
UV Luminescence (Fluorescence & Phosphorescence)
UV or x-ray fluorescence tests and phosphorescence tools are useful to identify lab-grown diamonds based on their glow patterns. These lab tools can detect subtle reactions under UV light. This test is good for identification when combined with other tests.
Advanced Lab Instruments
Lab-grade spectroscopy and imaging instruments are used by gem labs like GIA or IGI. A Raman spectroscopy is used to identify atomic structure. FTIR and photoluminescence spectroscopy identify treatments or growth origins. DiamondView reveals growth patterns to distinguish natural vs. synthetic diamonds. A refractometer measures the refractive index of the stone to see if it is the real thing.
Specific Gravity Test
A specific gravity test measures the density of the stone. Diamonds will have a high density which is greater than most simulants.
Grading and Certification
Grading and certification by a gem lab is the most conclusive method for determining a diamond’s authenticity. These labs (GIA, AGS, IGI) use many advanced tools to confirm authenticity and determine if it's a natural mined diamond or a lab-grown diamond. They assess the cut, clarity, color, carat of the diamond, and detect treatments. Shown below are GIA certified diamond earrings and a diamond ring.
Final Thoughts
Testing a diamond can start at home but should end with a professional diamond expert if you’re unsure–especially if the value is high. At-home tests can give you clues, but only a professional using lab tools can confirm a diamond’s authenticity, detect treatment, or determine lab vs. natural origin.
We at E.D. Marshall Jewelers welcome you to stop in at our jewelry store. Our professionals are ready and waiting to help you with an appraisal, finding a new piece of diamond jewelry, or even if you would like to sell a diamond. We can help you feel confident when investing in a diamond and settling curiosity about what you already own. We look forward to working with you!