Jewelry Blog

Do Diamonds Sparkle Rainbow Colors?

Customer examine diamonds in a diamond wedding band

If you’re buying jewelry, you might wonder if diamonds sparkle rainbow colors. You may question if the stones you like are even genuine. It might be hard to tell since there are so many choices available. 

Before making that purchase, you can find answers to your jewelry questions below. Find out what makes a diamond sparkle. Learn the difference between synthetic versus simulated diamonds and more. 

Do Diamonds Sparkle Rainbow? 

Genuine diamonds do not sparkle in rainbow colors inside of the stone. Instead, the inside of real diamonds sparkles in tones white and gray. The play on light in the diamond is brilliance. One factor that determines a diamond’s level of brilliance is the cut. 

Real diamonds sparkle rainbow colors when their light is deflected to other surfaces. In other words, colors shoot from the diamond when the direct light hits the stone. This flash of colors from a diamond is called “fire.” 

Of course, brilliant multicolor sparks are appealing to most jewelry lovers. Many of them focus on how the stone looks rather than its value. This works fine as long as they know they don’t own a real diamond. Unfortunately, some people are not aware that their diamond is not genuine. 

Light affects the way a stone sparkles, whether manufactured or genuine. However, synthetic stones can only imitate the brilliance of a genuine diamond. Diamonds reflect light in a way that is unique.

It is also important to note that pictures can sometimes capture colors as they are leaving the diamond, giving the impression that there is a rainbow.

Refractive Index 

11770 Customer using a Loupe on a Blue Diamond Double Halo Ring in Showroom

The amount of fire and brilliance in diamonds depends on where they fall in the refractive index. The refractive index measures the level that light bends when it passes from one medium through another. Simply stated, a stone with a higher reflection rate will disperse less light on the surface. Natural diamonds have a high infraction rate. 

Still, a pure diamond will light up like fireworks depending on its natural properties. A light that hits a diamond bounces around inside the stone and then exits. Therefore, the light is considerably livelier when it reaches the eye. Other factors, such as the cut, also affect diamond brilliance. 

At the same time, synthetic diamonds have a low refractive index. Light deflects differently in artificial diamonds. Unlike natural diamonds, sparkle rainbow colors show up inside synthetic stones. 

Simulant and synthetic diamonds are not the only stones with low reflective indexes. Sapphires and emeralds are among the precious stones low on the index. Although beautiful, opals are the least refractive gemstone. 

Diamond Cuts 

Cuts determine the amount of rainbow sparkles the stone will have. When you hear the “cut,” it refers to how the facets on the diamonds interact with light. Poor facet cuts will ruin a good diamond. A well-cut diamond is bright and full of fire. As such, it is essential to buy diamonds from reliable sources. 

Several factors determine the quality of the gemstone. 

First and foremost, gemstones are measured with a Cut Scale. Diamonds that are high on the scale are the most expensive. However, the price reflects the exceptional quality of the stone. 

An Ideal cut is the highest on the scale. Diamonds with this cut are brilliant and sparkle with rainbow colors the most. Yet, the Diamond cut next on the scale is a very close second. The next cut is called an Excellent. The craftsmanship on this diamond is almost as outstanding as an Ideal cut stone. 

Additionally, Very Good cuts are an excellent choice and popular because they are a lower price. Good cuts are comparable to Very Good cuts in quality and price. 

On the other hand, Fair cuts are considered average on the Cut Scale. 

The Poor stone cuts are the cheapest option and last on the Cut Scale. This cut has a low level of brilliance and light. 

The position of the cut is another factor in how much light is dispersed. However, it is not to be confused with the ratings from the Cut Scale. An ideal cut scatters the most light, while a deep cut also deflects a good deal of light. In contrast, shallow cuts disperse light mainly along the sides of the diamond. 

Finally, a stone’s shape also impacts the amount of fire it brings. Round brilliant is the facet pattern that returns the most light. It has fifty-eight facets. For this reason, it is the most popular shape for engagement rings. 

Lab-Grown Diamonds 

lab grown diamond machine HTHP

Natural diamonds are mined from the crust of the earth. By contrast, humans create lab-grown diamonds under controlled conditions, and technology duplicates the conditions under which natural diamonds grow. Further, they consist of carbon atoms arranged in the diamond crystal structure. 

Other names for lab-grown stones are synthetic, engineered, and cultured diamonds. They exhibit the same chemical and optical properties as mined diamonds. As such, lab-grown diamonds sparkle rainbow colors in the same way as earth-grown stones. 

Engineered diamonds are considered “real.” However, the price is about 30% less than natural diamonds. Additionally, synthetic diamonds are an earth-friendly alternative to mined diamonds. For these reasons, millions of people buy jewelry created with synthetic stones. 

Important Note: We strongly caution buyers against buying lab-grown diamonds. Read our complete review on why lab-grown diamonds are a massive scam!

Simulated Diamonds 

Lab Grown Diamond Machine

Diamond simulants are a big business around the world. Higher-end synthetic diamonds look real at first glance, but they are a fraction of the price of a natural stone. Most notably, some synthetic diamonds sparkle rainbow flashes that are too eye-catching to resist. 

These simulated diamonds are white stones that come in two overall categories. 

First is the simulated diamonds that are made with clear natural gemstones. This includes white zircon, white sapphire, and white topaz. Other natural diamond simulants are moissanite and glass. All of these stones come from the earth. However, their chemical, physical, and optical properties are different from diamonds. 

Synthetic stones fall into the second diamond simulant category. Cubic zirconia and Yttrium Aluminum Garnet (YAG) are the most common. Cubic zirconia is an inexpensive mineral made from zirconium dioxide. Although the stones look like diamonds, they do not have the same carbon structure. 

The mineral YAG was first grown in the 1950s and was the diamond simulant of choice until cubic zirconia arrived. Contemporary varieties of YAG are available in clear and other colors which look like semi-precious stones. 

Important Note: As with lab-grown diamonds, we caution buyers against buying synthetic or simulated diamonds. Read our complete review on why fake diamonds are a massive scam!

How to Check if a Diamond Is Real? 

Real Diamond on Newspaper

The type of diamonds you buy is a personal choice. Some people purchase inexpensive stones to wear on vacation so the real ones won’t get lost. At the same time, earth-conscious buyers prefer vintage or used stones. They may choose manufactured diamonds as well to protect the environment. In addition, simulated diamonds are the more affordable option for budget-conscious buyers. 

But what if you are unsure if a stone you already own is natural? 

Some factors indicate whether your diamond is authentic. For instance, if your diamonds sparkle extremely bright rainbow colors, they may not be real. Cubic zirconia is one example of a synthetic diamond that looks too good to be true. 

Another way to test for a mined diamond is to breathe on the stone. Watch if the diamond fogs up a lot. Then, see how long it takes to evaporate. A real diamond will only fog up a little bit. The condensation will quickly disappear. 

Furthermore, a genuine diamond will not scratch because it is the hardest stone. You can check your stone by gently scraping it with a knife. Remember to do this only if you want to take the risk, but you’ll know you have a synthetic diamond if the stone scratches. 

Another test you can perform at home is whether the stone floats. Exposing the diamonds to extreme temperatures is yet another test. Some people take an intense route and try to shatter their diamonds. 

Lastly, you can purchase a diamond selector tool. The device determines if a stone is synthetic or genuine. 

However, the most accurate and safest way to verify your diamond is to take it to a trusted jeweler. A professional jeweler will use the right tools and equipment, and you will benefit from their experience and education. Most of all, you get the correct information about your diamond.

Click here to read our complete guide on how to tell if a diamond is real or fake.

Buyer Beware 

Diamond Engagement Ring Customer from Estate Diamond Jewelry Showroom

Perhaps you have your eye on a unique piece of jewelry in a store. You might have even asked to try it on. However, you may wonder if the diamond is real in the back of your mind. You are not alone. That scene plays out repeatedly each day. It is hard to tell if a stone is real or synthetic with many available choices. 

However, you can be proactive in making sure you buy the diamond you expect. If the diamond seems too good to be true for the price, it probably is. Always purchase jewelry from a well-known, respected dealer. And don’t hesitate to ask for a gem report from a laboratory if none is available. If they don’t cooperate with the request, you may want to consider finding another jeweler. 

Finally, remember that the type of diamond you choose is your personal decision. Wearing jewelry should be enjoyable. Just be sure you are getting what you pay for and have fun.

Talk to a Diamond Expert

Do you have any additional diamond questions? Or are you in the market to buy a diamond? Feel free to reach out to our diamond experts. They will respond as soon as possible.


About Afshin Shaddaie

Afshin moved to New York City in the 1980s, and a few years later, he began his career in the fine and rare jewelry scene. He teamed up with Michael Khordipour, and they've been curating vintage jewelry ever since. He also regularly contributes to Forbes, Rapaport, CNBC, The Knot, and Insider. Afshin constantly travels to international shows and private viewing events in the hope of finding rare vintage rings that will be important enough to make an impression. He is available for appointments at our New York showroom when he's not traveling. In 2019, Afshin authored his book called The Engagement Ring Guide for Men. He is considered one of the world's foremost authorities on vintage jewelry and antique diamonds. His favorite jewelry era is Art Nouveau, and he loves rare Italian jewelry from the 1950s - 1970s. The Natural Saltwater Pearl is his favorite precious jewel.