The short answer is no, lab-grown diamonds do not glow in the dark. The reason for this is that diamonds, whether they are natural or lab-grown, are made up of carbon atoms that are arranged in a specific crystal structure known as a diamond lattice.
Diamonds that belong to a group called type IIB usually look blue. After they absorb high-energy light like UV light however, type IIB diamonds glow in the dark for a short time. This afterglow refers to the phosphorescence of a diamond which ranges in colour from blue to pink and fiery red, depending on the diamond.
Fake diamonds, on the other hand, will glow other colors or not at all. While an extremely high quality gem will also not glow under UV light, this can be a good test for questionable stones if done in consultation with a trained jeweler.
Yes, diamonds can glow in the dark due to fluorescence, and you can only see this blue light under ultra-violet (UV) light. Around 30% of diamonds have this natural fluorescence feature. In natural daylight, blue fluorescence will make a diamond look whiter, even if it's slightly yellowish.
Black light test:
When you place a real diamond underneath an ultraviolet light, the stone with fluorescence in it will turn blue. But it's important to know that this will only happen with about one-third of all diamonds. A fake diamond, on the other hand, will almost never look blue under a black or UV light.
Placing a diamond under UV light and watching the reaction can sometimes be a good indicator of whether a diamond is real or not. Most diamonds emit a blue-colored glow under UV light, but not all of them. So if your diamond does, you can feel pretty confident that it is a real diamond.
A real diamond appears gray and white inside (brilliance) when held to the light and can reflect rainbow colors (fire) onto other surfaces. A fake diamond will display rainbow colors within the stone when held up to light.
Only about 25% to 35% of diamonds exhibit some degree of fluorescence in reaction to long-wave UV light. More than 95% of these diamonds fluoresce blue.
Hold it in the light to see how it sparkles.
A fake diamond will have rainbow colors that you can see inside the diamond. “People have a misconception that diamonds sparkle like a rainbow, but they don't,” Hirsch said. “They do sparkle, but it's more of a gray color.
The Floating Test
Drop the diamond into the water. True diamonds have high density and should quickly sink to the bottom of the glass. Fake diamonds are not as thick, and therefore, more likely to float in water.
99% of the time, the glow is blue, but on rare occasions, diamonds glow white, yellow, green, or even red in color. Depending on the diamond, fluorescence can either improve the diamond's color or make it appear hazy or milky.
FACT: Absolutely not. The presence or absence of fluorescence should not be used as a DIY test to determine if your diamond is real. First, not all natural diamonds fluoresce under the standard UV lamp used by gemologists (see Myth #1). Second, some synthetic or lab grown diamonds do fluoresce to these wavelengths.
Once your black light is turned on, hold the stone under the UV light. Most diamonds will have a blue-colored glow, but if you see the slight green or yellow fluorescence instead, you'll need to seek the opinion of a professional jeweler as this may mean your stone is not genuine.
No, cubic zirconia does not shine with the same brilliance as a diamond. Diamonds shine with pure white light, while CZ diamonds give off rainbow colors. They are also more prone to becoming dull and scratched over time, and are thus not the best option for daily wear.
Moissanite disperses light very well and has higher light refraction than diamond, and will appear more brilliant. Additionally, moissanite is less likely to attract grease or dirt over time than a diamond due to its crystalline structure, which should help keep the 'sparkle' longer between cleanings.
Sometimes, tiny amounts of impurities in diamonds can cause them to glow or luminesce under UV light. UV diamond fluorescence occurs in about 35% of colorless (white) diamonds and can be faint or very strong. (Fluorescence is a type of glow that occurs almost immediately after exposure to UV light).
This water test is easy if you have a loose diamond: Get a glass and fill it with water (it doesn't matter what type of water you use). Drop the diamond into the glass of water. Due to the high density of diamonds, when dropped into the water a real diamond will sink.
In cut stones, cubic zirconia tends to have dull, rounded edges, while diamonds' facets stay sharp. Diamonds rarely show polish marks, but if they do, they will be in different directions on different facets. On the other hand, cubic zirconia will show polishing marks in the same direction on adjoining facets.
Moissanite is not made from carbon like diamonds – instead, it is made of silicon carbide and has its own unique physical properties. The beauty of moissanite is that it comes with all of the advantages of being a real gemstone and just happens to look very similar to a diamond!
Usually fluorescence is blue in color. Less often, a diamond can have yellow or even white fluorescence (other colors too). Diamonds with Strong - or Very Strong - fluorescence can appear quite cloudy, milky or hazy to the naked eye, and emit a prominent and saturated glow in the presence of UV light.
An ideal cut diamond shows only a few intensely bright flashes in direct sunlight. A diamond that actually looks good in sunlight splits those few flashes up into ten or twenty smaller sparkles.
A diamond will become fluorescent if there are traces of the mineral boron present in the earth during the crystallization process. Diamonds can fluoresce in a variety of colours – blue, yellow, green, orange and white – but blue is the most common.
Any diamond will flash, sparkle and look the best in direct sunlight. So, if you really want to know what exactly a diamond looks like, you must observe it in natural daylight. This is when its true brilliance and sparkle can be noticed. This is why most dealers sort their diamonds in indirect sunlight.
Most synthetic diamonds look too good to be true all due to their extreme brilliance. Does your stone look really bright with lots of rainbow reflected colors? If so, it's most likely cubic zirconia. Yes, real diamonds are brilliant, but they are much more subtle than synthetics.