How to Tell if a Diamond is Real: Ultimate Guide to Tests and Tips

When buying a diamond ring, engagement ring, or any piece of diamond jewelry, one of the most common questions that come to mind is: Is this diamond real or fake? Whether you’ve inherited a piece of jewelry or are simply curious about a potential purchase, determining the authenticity of a diamond is important for both financial and sentimental reasons.

In this article, we’ll explore the different ways to tell if a diamond is real, highlighting the most common tests and tips that anyone can use - whether you’re at home or in a jewelry store. From the classic water test to the more scientific diamond testers, we’ll cover the most effective methods to distinguish real diamonds from fakes.

What is a Real Diamond?

A real diamond is a naturally occurring gemstone composed of carbon atoms arranged in a crystal structure. Diamonds are formed under extreme pressure and temperature conditions deep within the Earth, making them the hardest known natural material.

Real diamonds possess unique qualities, such as incredible brilliance and fire (the dispersion of light into various colors), as well as remarkable hardness. These characteristics make diamonds incredibly valuable and sought after. Synthetic diamonds, also known as lab-grown diamonds, share many of these same qualities but are created through human-made processes, making them more affordable than naturally mined diamonds.

While natural diamonds and lab-grown diamonds are chemically identical, there are ways to differentiate between the two, which can affect their value. Natural diamonds come with inclusions and imperfections formed over millions of years, while lab-grown diamonds are typically cleaner with fewer inclusions. 

What Are the Common Fake Diamonds?

Fake diamonds come in various forms, but the most common are cubic zirconia and moissanite.

• Cubic Zirconia (CZ) is the most widely known imitation of a diamond. It is often used in jewelry as a cheap substitute due to its optical appearance resembling diamonds. However, CZ lacks the hardness and durability of a true diamond and can be easily scratched.
• Moissanite, while appearing similar to diamonds, is chemically different. Moissanite has a higher refractive index than diamonds, meaning it can appear more sparkly. However, it is not a diamond, and although it is a beautiful gemstone, it’s not as valuable as a natural diamond.

The challenge lies in differentiating these fake diamonds from the real deal, which is where diamond testing methods come in handy.

How to Tell if a Diamond is Real Using the Fog Test

One of the simplest ways to check if a diamond is real is by performing the fog test. Here's how:

1. Hold the diamond between your fingers.
2. Exhale onto the surface of the diamond, creating a fog (similar to how your breath fogs up a mirror).
3. Observe: A real diamond will clear up almost instantly because of its high thermal conductivity. A fake diamond, like cubic zirconia, will remain cloudy for a longer time because it does not conduct heat as effectively as a real diamond.

The fog test is an easy way to tell if a diamond is real at home without special tools.

How to Use Water to Test a Diamond’s Authenticity

The water test is another simple method to check if your diamond is real. Here’s how you can perform the test:

1. Fill a glass with water.
2. Drop the diamond into the glass of water.
3. Observe: If the diamond sinks to the bottom of the glass, it’s likely real. Fake diamonds, such as cubic zirconia, often float due to their lighter weight.

This test works because diamonds are denser than most other stones, including fake diamonds like cubic zirconia and glass.

The Paper Test: A Simple Way to Test Your Diamond

The paper test is another quick, at-home method. Here's how you can perform it:

1. Place a piece of paper with small text or a printed pattern underneath the diamond.
2. Look through the diamond from the top.
3. Check for visibility: A real diamond will not allow you to see the text or pattern clearly. The high refractive index of diamonds causes them to bend light, distorting what you see. A fake diamond like cubic zirconia will show the pattern clearly because it does not bend light in the same way.

This test relies on the unique optical properties of diamonds to differentiate them from imitation stones.

How to Tell if Your Diamond is Real Using a Magnifying Glass

A magnifying glass is a helpful tool for inspecting diamonds. Here’s what to look for:

1. Inspect the diamond closely using a magnifying glass (ideally 10x magnification).
2. Check for inclusions: Real diamonds often have small imperfections or inclusions inside them, which are unique to each diamond. These can appear as tiny bubbles, scratches, or other marks that you won’t find in a fake diamond. Cubic zirconia, for example, is typically flawless or has smooth edges.
3. Look at the edges of the diamond: Real diamonds have sharp, clean edges, while fake diamonds often have rounded, smooth edges.

Natural diamonds generally have more imperfections, which make them unique and easy to identify under magnification.

Using UV Light to Identify a Real Diamond

Another way to test if a diamond is real is through UV light. Here’s how to conduct this test:

1. Take the diamond into a dark room.
2. Shine a UV light (black light) onto the diamond.
3. Observe the glow: Real diamonds will typically glow blue under UV light, while fake diamonds like cubic zirconia may not glow at all or could show a different color.

The fluorescence exhibited by a real diamond under UV light is one of its unique traits.

The Diamond Tester: How Accurate Is It?

A diamond tester is a tool that measures the thermal conductivity of a diamond. It is often used by jewelers and professionals to determine whether a diamond is real or fake. Here’s how it works:

1. Place the diamond on the diamond tester’s sensor.
2. Activate the device: A real diamond will register as genuine on the tester, usually producing a sound or color signal indicating it is authentic. Fake diamonds or simulated stones won’t trigger the tester or will show a different reading.

A diamond tester is one of the most accurate methods for testing a diamond’s authenticity.

Professional Methods for Testing a Diamond’s Authenticity

For the highest level of certainty, a professional diamond tester will use a combination of tools and techniques to assess the authenticity of a diamond. Jewelers may use advanced equipment like microscopes, diamond graders, and conductivity testers to examine the diamond’s clarity, inclusions, and thermal properties.

Professional graders, like those certified by the Gemological Institute of America (GIA), can certify diamonds by examining their cut, clarity, color, and carat weight - the 4Cs of diamond grading.

Knowing how to tell if a diamond is real is important when buying or inheriting diamond jewelry. Whether you use an at-home test or a professional service, you’ll be able to make sure your diamond is the real deal.