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Do Real Diamonds Shine In The Dark?

Do Real Diamonds Shine In The Dark?

Aside from being one of Earth’s hardest materials, diamonds exhibit extraordinary beauty. The most sought-after gemstone in the jewelry world earned its popularity due to its brilliance – the ability to reflect light in such manners that leave everyone breathless. 

Some of you may be asking: Do real diamonds shine in the dark?

The answer to this question is simple: 

No, diamonds don’t shine in the dark. Diamonds need a source of light to sparkle. However, there is a specific condition where diamonds can “glow” in the dark due to their impressive abilities.

What is this condition? What are these abilities?

We’ve covered all of the answers in this article. Without further ado, let’s find out more about diamonds and what makes them sparkle!

What Makes A Diamond Shine? 

When diamonds are found, they’re certainly not well-cut shining gemstones that you’d see in jewelry. Instead, freshly mined diamonds have rough and opaque surfaces

You need to remove the outer layer by polishing and cutting the diamond to make it shine. In addition, two factors are considered – refractive index and dispersive power. 

The refractive index is the one that is responsible for a diamond’s brilliance. Dispersive power is the ability that allows splitting white light and reflecting additional colors.

Scintillation brilliance is applied to the arrangements and number of light reflections from the internal facets representing the sparkle. The diamond fire is determined by the cut’s crown height and size, angle, and the number of facets in the diamond

Diamond’s brilliance is an integration of proportions and angles. It shows off the diamond’s light return based on how the light enters, bounces within the diamond, and returns to our eyes. 

With that said, diamonds will sparkle only in the presence of light. And poor light return from a diamond usually lacks beauty.

The brilliance consists of several factors, all based on patterns and faceting. But how can that brilliance be optimized in diamonds? 

It’s usually a combination of table facet, girdle, pavilion depth, total depth, culet, and crown angle.


When a diamond is tilted and rocked at different angles, some light reflects on the surface of the facets rather than bouncing inside the diamond. That is known as reflection. 

Usually, around 17% of light is reflected by the diamond. Reflection should be balanced; when the facets are too big, you can see reflections strengthen or weaken too much. That will cause the diamond to look dull.


The perfect diamond is cut so that light enters it, bounces around, and exits from the top of the diamond. That occurrence is known as refraction

Diamonds have their sparkly characteristics due to them scoring high on the refractive index, a 2.41 to be exact. With perfect cutting, the refraction is highly noticeable. With a diamond that’s cut well, light reflects ideally within the stone.


As you may already know, diamonds aren’t black and white. Instead, they are reflecting a whole specter of rainbow colors from within. That’s a result of dispersion. 

Diamond’s dispersion is measured at 0.44 as the light bounces around inside, bends, and then exits to our eyes. Dispersion is more commonly known as fire. The sight of these colors is what gives a diamond its unique beauty.

Other gemstones don’t have the same gorgeous dispersion that diamonds have. That’s why these precious stones are still the most popular choice for engagement rings and jewelry.

Learn More:

Diamond’s Cut 

Diamonds are cut to maximize the fire, brilliance, as well as overall visual beauty of a diamond. The cut is a measure of light presentation as light hits a diamond. 

Here’s what happens: As light hits a diamond, it penetrates the diamond, bounces, and reflects within the diamond, after which it returns to the viewer’s eyes. That is the sparkle that we see and love. 

The cut of a diamond impacts the amount of light presentation achieved. Additional factors, like the sizes, shapes, angles, and locations of facets, will determine the famous diamond sparkle.

Once a diamond is cut, its cut can be graded. Gemological Institute of America grades cut base measuring the sizes and angles of facets of a diamond. These include the diamond’s depth, table, pavilion, girdle, cutlet, and crown.

These factors come together to determine the diamond’s cut grade. 

Each diamond size and shape has an ideal cut proportion. If you want an ideally cut diamond, do some research and find examples of diamonds with perfect proportions.

The Cut Scale

Diamonds earn a “Fair” or “Poor” grade when they have significant light leakage. 

These diamonds are leaking a noticeable amount of light from being too shallow or too deep in height. Diamonds with these grades have little brilliance and are overall less visually appealing.

Well-cut diamonds that are graded as “Good” possess high degrees of sparkle. 

They have some light leakage, but all in all, they shine bright. These diamonds can have larger – or even smaller – measurements than perfectly cut diamonds with the same shape.

Very well-cut diamonds that capture most of the light are graded with “Very Good.” These are very brilliant and have minimal light leakage. 

The highest grade representing the best diamonds in the world is “Excellent.” 

Diamonds that earn this rating are masterfully crafted and cut with such precision that they can unleash maximum brilliance and sparkle. They have little to no light leakage. Also, this category represents the top 3% of all diamonds.

Diamond Shapes With The Most Facets

Brilliant cut diamonds are designed to have the most facets and the most shine. Modern round brilliant diamond cut is the most popular. Classic round shape in pair with numerous facts grabs the light better than other shapes. 

These modern round brilliant gemstones exhibit the most brilliance possible. Even adding more facets doesn’t improve the shine and luster.

Some other shapes that are cut with brilliant design are:

Diamond Fluorescence 

When you think of fluorescence, you may think of a dark room with ultra-violet light illuminating neon posters – or perhaps dancing at a rave and being hypnotized by the glowsticks? 

Well, either way, that’s not the kind of fluorescence we’re talking about here. 

Fluorescence is the attribute of a diamond that is misunderstood the most, and yet, it is simply the diamond’s reaction to black light (UV light). 

Diamonds will glow or radiate blue color in the blacklight environment. Most of them emit blue color, but in some instances, this glow can be green, yellow, white, or even red. 

Fluorescence can be found in around 30% gem-quality diamonds. A diamond’s ability to glow in a UV environment comes from inclusions. However, there is still no material evidence for what exactly causes fluorescence.

Some studies have proven that fluorescence has no impact on the diamond’s appearance. The structural integrity isn’t affected by fluorescence. The presence of inclusions in the diamond that cause fluorescence doesn’t weaken the binding of carbon. 

Learn More: Can Ultraviolet (UV) Light Destroy A Diamond?

Fluorescence Grading

The Gemological Institute of America established a scale on which diamond fluorescence is graded. Note that fluorescence seems to impact diamond’s visual appearance in about 1% – or even less – of all cases.

As we mentioned earlier, fluorescence is usually blue in the glow, but sometimes you can find diamonds with a white, green, yellow, or red glow. 

That is very rare, though, and can have the same impact on the diamond as a blue glow.

First, we have diamonds exposed to UV light with no soft, blue glow emitted. These diamonds have no traces of elements that cause fluorescence. 

Non-fluorescent diamonds have the most significant premium; they are highly desired and pretty expensive.

The diamond with minor traces of elements that cause fluorescence will emit a faint, soft, blue glow when exposed to UV light. There’s no impact on the diamond. 

“None” and “Faint” fluorescence have almost the same effects on diamond’s value.

Diamond exposed to UV light that emits a light blue glow is graded with the “Medium.” These diamonds are excellent as the medium fluorescence reduces the diamonds price. It can also improve the color of lower grades such as J, K, or L.

When a deep blue glow is emitted in UV conditions, diamonds are graded with “Strong.” 

That kind of fluorescence can improve lower colors such as J, K, or L. On the other hand, it can harm high-color diamonds such as D and E, resulting in a slightly grayish appearance.

A very bright blue glow emitted when the diamond is observed in a UV environment means that it’s graded with “Very Strong.” The diamond’s appearance can be affected by this, as the strong fluorescence makes a diamond look hazy or gray. 

Read More: Do Diamonds Emit Light?

Effect On Sparkle And Price

Fluorescence rarely has any effect on a diamond’s sparkle. However, it’s generally advised that consumers avoid fluorescence in high colors such as D, E, and F. 

But you’re free to consider fluorescent diamonds in colors such as I, J, K, and L. 

The lower colors can visually appear one grade higher because of the fluorescence. You’ll also find that fluorescent diamonds usually come with a 10% to 15% discount against “None” or “Faint” fluorescent diamonds. 

Fluorescence rarely affects a diamond’s appearance, though. GIA measures it for transparency purposes. 

In fact, a study conducted by GIA shows that fluorescence doesn’t have a notable impact on the diamond’s appearance. So, this characteristic shouldn’t be a major deciding factor when you’re choosing your diamond.

Regarding fluorescence, the most difficult decision in selecting a diamond is whether to chose “None” or “Faint” and “Medium” or “Strong.” It basically doesn’t matter. The difference and effect on the diamond’s sparkle are more or less unnoticeable. 

So, we recommend you go with the option that offers you the best price.

Is Fluorescence Bad? 

Gemological Institute of America has extensively studied fluorescence and whether it impacts a diamond’s visual appearance. After years of testing, they concluded that there is no material effect on the visibility and sparkle. 

That is mainly true, but still, there are about 1% instances where fluorescence has an impact.

There are examples of fluorescence enhancing the diamond’s beauty. 

Strong or medium fluorescence in diamonds with a warm yellow tint can sometimes make the diamond appear whiter and remove some yellow hue. The difference is minor, so it won’t make a J color diamond look like a D or E color. 

In a very small number of cases, though, when a diamond is one of higher colors, the extra whitening effect can unfavorably affect the diamond.

There are cases where diamonds with a “Very Strong” blue fluorescence can reveal a milky, hazy, or grayish look. It can darken or dull the diamond in strange ways.

In the end, it’s important to mention that fluorescence doesn’t affect the structural integrity of the diamond. It’s a diamond’s side effect, nothing more.


If you’re still not sure what the answer is to the question “Do real diamonds shine in the dark” let us break it down for you. 

Diamonds need a source of light to shine, so the answer to the question would be: No, diamonds don’t sparkle in the dark.

Diamonds’ characteristic responsible for their shine is called brilliance. Two factors that are taken into consideration regarding the brilliance are the refractive index and dispersive power. 

Refraction is an occurrence where light enters, bounces around, and then leaves the diamond. Perfect diamonds are cut in such ways to maximize this ability.

Dispersion is a diamond’s ability to reflect the light in a specter of rainbow colors. Other gemstones don’t have the same dispersions as diamonds do.

However, some diamonds do shine in the dark – but only when they’re exposed to UV light. This ability is called fluorescence, and it doesn’t impact a diamond’s appearance, nor does it affect a diamond’s structural integrity.