Has this ever happened to you? You’ve come into a piece of diamond jewelry, but you’re not exactly sure if it is indeed a diamond. Maybe you inherited a family heirloom or purchased a diamond for a suspiciously low price, or someone gave you a gift. You start to wonder what it’s really worth. Is this the real thing? Is there any way to truly know?
First of all, what do we mean by “real”? The word “diamond” describes a mineral crystal composed of at least 99.95% carbon. A real diamond can be grown in the upper mantle, the layer of the Earth below the crust, over the course of millions of years, or in a laboratory over a few weeks, either by a process called High Pressure, High Temperature (HPHT), which mimics the hot, pressurized environment in which natural diamonds grow, or Chemical Vapor Deposition (CVD), a process by which carbon atoms are added layer by layer to a diamond seed inside of a vapor-filled chamber.
The following methods will tell you whether or not your stone is a diamond, but many of them won’t tell you if that diamond came out of the ground or out of a laboratory. That’s a much more difficult distinction to make, requiring an expert gemologist to use technology that is not commercially available. But if you want to determine whether your diamond is a diamond and not glass or some diamond imitation like cubic zirconia or moissanite, here are a few simple tests you can try at home.
The Electronic Test
The simplest and most accurate way to determine the authenticity of your diamond is to purchase an electronic diamond tester. You can buy these on Amazon, and they are relatively inexpensive. These devices heat the diamond and measure the rate of thermal conductivity to determine whether or not the stone is a diamond.
Newspaper “Read-Through” Test
Place your diamond on a newspaper. If you can read the writing through the diamond then it is likely that your “diamond” is actually quartz or glass. This is because diamonds are not actually transparent: they have a high refractive index and dispersion of light, which means they bend and reflect incoming light, making it difficult to see through them. These properties make diamonds appear brighter and more colorful than plain glass.
The Fog Test
A diamond is very good at dispersing heat. The “Fog Test” involves holding the diamond up to your mouth and exhaling, like you would when cleaning your glasses or a mirror. A real diamond will evaporate the fog immediately. If the fog stays on the diamond for more than 3-4 seconds, you may be holding a fake diamond.
The Weight Test
Use a carat or gram scale to weigh your diamond. Fake diamonds will normally be 50-60% heavier than authentic diamonds of the same size.
The Rainbow Test
Look closely at your diamond’s sparkle. Do you see beautiful shifting shades of gray, or do you see many rainbow reflections? If you see many rainbow reflections, you either have a fake or a low-quality diamond.
The UV Test
This is a good test for people who have access to ultraviolet light or black light. Place the diamond under the UV or blacklight in a dark room. If the diamond is real, it should have a blue fluorescent glow. If you see a green, yellow, or gray fluorescence, the diamond could be fake. If the diamond does not exhibit any fluorescence (it does not glow any color under UV light), that does not mean the diamond is fake. You may simply have a higher-quality diamond.
The Flaw Test
Diamonds tend to have tiny flaws in them such as small cracks, traces of carbon or other elements, or pinpoints. These flaws are called inclusions, and too many of them can affect the clarity of the diamond. The fewer inclusions in the diamond, the higher it scores on the clarity chart. You can use a magnifying glass to check for these tiny imperfections. If you can’t see any, you either have a lab-grown diamond, a fake diamond, or an extremely rare flawless diamond.
The Metal Test
If your diamond is set in a ring, check the shank for a hallmark. The shank is the part of the ring that encircles the finger, while the hallmark is a stamp that may contain information about the manufacturer, the type of metal used, and the composition (i.e. “925” for sterling silver or “999” for 24 karat gold), the place of manufacture, or the type of stone used. If the hallmark reads “CZ,” your stone is cubic zirconia and not a diamond.
The Water Test
Diamonds are denser than water. If you have a loose diamond, you can drop it into a glass of water. If it sinks, then it is a real diamond. If it floats above or just below the surface of the water, your diamond is likely a fake.
The Loupe Test
Another inexpensive jeweler’s tool that you can purchase and use is a loupe, those little lenses jewelers hold up to their eyes to inspect jewels. A loupe will let you clearly see a diamond’s inclusions. Glass imitations, lab-grown diamonds, or gemstones that imitate diamonds like cubic zirconia do not generally have inclusions.
The Jeweler Test
While none of the above tests are 100% definitive on their own, performing a few of them can allow you to say with some certainty that your stone is or is not a diamond. The only place to get a definitive answer is from a professional at your local jeweler. Gemologists have the training, experience, and equipment to tell you exactly what your stone is made of. Not only will they be able to tell you if your stone is a diamond or an imitation stone; they will be able to tell you if your real diamond came from a mine or a laboratory.
