The primary difference between a real diamond and a fake diamond is that the real diamond forms naturally over thousands of years, whereas a fake diamond is created artificially in a lab. Basically, a real diamond is natural, whereas a fake diamond is man-made.Diamonds are one of the most popular gemstones in the world. They are known for their clarity and their fire, which is the way it shines when hit by light. It is often believed that the value of diamonds comes from the fact that they are so rare, however, that is not the truth. Diamonds are actually quite common. Their value comes from their popularity. If people are willing to pay for it, then companies will charge for it.

Diamonds are popularly classified through 4 Cs: color, cut, clarity, and carat. There are many different types of diamonds, most are clear, but due to small defects they also come in a number of colors, such as yellow, pink, blue, etc. They also come in various clarities. Some are cloudy, others are clear. Cloudy diamonds have less demand as they don’t tend to shine alot. Another commonly held misconception for diamonds is that higher the carat and better and more expensive the diamond. However, that is not the case, cut is more important than carat. A diamond of a smaller carat but which is brilliantly cut, will cost  more and look better than a diamond which is of a higher carat but is poorly cut. The clearer their color and clarity, the higher their carat, and better their cut, the more their cost.

Here is How to Tell if a Diamond is Real or Fake

Water Test

Use this simple test to ensure a diamond is real.
Find a normal sized drinking glass and fill it ¾ of the way with water. Carefully drop the loose stone into the glass. If the gemstone sinks, it’s a real diamond. If it floats underneath or at the surface of the water, you have a fake on your hands. A real diamond has high density, so the water test shows if your stone matches this level of density.

Fog Test

For the fog test, hold the diamond or ring between two fingers and breathe on it with a puff of air. A light fog will form on the diamond because of the moisture and heat in your breath. If the fog dissipates right away, the diamond is real. If it takes several seconds for the fog to disperse, it is likely a fake diamond. Diamonds effectively conduct heat and therefore disperse heat quickly.

Magnifying Glass

To determine if your diamond is real, hold a magnifying glass up and look at the diamond through the glass. Look for imperfections within the stone. If you're unable to find any, then the diamond is most likely fake. The majority of real diamonds have imperfections referred to as inclusions. There are flawless diamonds out there, but they're either lab-created diamonds or pretty pricey given the unusually high quality.

Black Light Test

You'll need a black light for this one, obviously. Once you have it, turn off the lights and hold the diamond in front of the black light. Most diamonds will reveal blue fluorescence under a black light; therefore, you'll see a medium to strong color of blue, which means the diamond is real. If you don't see the blue color and instead see a slight green, yellow or gray fluorescence then this usually indicates the gem is not a real diamond. But remember: This is not a conclusive test and not all real diamonds will reveal a blue fluorescence.

Heat Test

To conduct the heat test, use a pair of pliers to hold the loose diamond while you heat it up with a lighter. After 45 seconds, drop it into a glass of cold water. A real diamond has a high resistance to heat and is one of the strongest materials on earth and so it will remain unaffected by the extreme change in temperature. Whereas, a fake diamond made of glass or zirconium, will shatter.

Dot Test

A real diamond will refract light—this is what gives it sparkle and brilliance. To test your stone's reactivity, take a piece of paper and draw a small dot on it. Place the diamond over the dot and see if you can see the dot through the stone. If the diamond is real, then you won't be able to see it as the image is refracted. You can also conduct a similar test using a newspaper. Place the diamond flat-side down and if you can see the black type through the stone then it's probably fake. On the other hand, a real diamond will refract the image and so you will not see anything through the stone if it's the real thing.

Scratch Test

The scratch test was a once widely used technique that aimed to determine the hardness of a gemstone’s mineral. The test involved scraping the loose gemstone along a mirror to see if it would scratch the mirror or the stone.

While a diamond is formed with very strong materials, fakes like cubic zirconia and moissanite are quite durable and scratch-resistant as well. For these reasons, the scratch test is not accurate. You are better served to use other tests such as a thermal conductivity test or having the diamond inspected with a professional loupe tool.