How to Identify a Black Diamond: Tests, Characteristics & More

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Determine if your “carbonado” is real or fake with this guide

Co-authored by Dan Hickey Reviewed by Cory Schifter

Last Updated: April 5, 2024 Fact Checked

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At-Home Tests

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Real Black Diamond Qualities

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Types of Black Diamonds

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Where do black diamonds come from?

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Interesting Facts

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Tips

Natural black diamonds are fairly rare and have unique qualities to look for—namely a large number of inclusions, an opaque black or very dark brown color, and imprecise cuts and edges. Thankfully, if you’re still not sure if it’s real, you can perform the same easy fake-finding tests you’d use on a regular diamond to determine its authenticity. In this article, we’ll walk you through exactly how to identify a black diamond and tell if it’s real, plus explore how they’re formed and other interesting facts about them.

Things You Should Know

Genuine, natural black diamonds contain many fractures and inclusions visible with a magnifying glass and are black or very dark brown or green.
Drop the diamond into a glass of water. If it sinks, it’s real. If it floats, it may be a fake.
Or, breathe on the diamond to fog it up. The fog will disappear right away from a real diamond, but will take several seconds to fade from a fake.

Section 1 of 5:

Testing if a Black Diamond Is Real or Fake

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1
Water drop test Fill a drinking glass about three-quarters full of water, then gently place the diamond into the glass. A genuine black diamond will sink to the bottom of the glass, while a fake stone may float just underneath the surface or on top of the water.^{[1]
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- True diamonds have a high density and always sink in water. Some popular fake materials for black diamonds, like moissanite or cubic zirconia, might float if the stone is small enough (although this is not a foolproof method to determine if the diamond is real or not).
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Dot test Lay a white piece of paper flat on a hard surface and draw a small dot with a pen. Then, lay the flat side of the diamond on top of the dot and look down on the paper through the pointed end. If you can see a circular reflection of the dot inside the gem, then it is not a real diamond. If you can’t see a reflection or the dot itself, then the diamond is real.^{[2]
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- Real, natural diamonds have refractive qualities that scatter light so much, it’s impossible to see letters or dots through them.
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Fog test Hold the black diamond (or the piece of jewelry it’s laid in) between two fingers and breathe on it with a puff of hot air. The heat and moisture of your breath will cause a light fog to form on the diamond. If the diamond is real, the fog will disappear immediately, whereas it will take a few seconds for the fog to dissipate on a fake.^{[3]
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- Real diamonds are incredibly efficient heat conductors that will disperse the heat from your breath right away.
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Heat test This test might destroy the stone if it turns out to be fake, so don’t perform it if you’d like to keep the gem afterward. Hold the stone over a flame from a candle or lighter with a pair of pliers for about 40 seconds to heat it up. Then, drop the diamond directly into a glass of cool water. If the gem cracks or shatters, it’s definitely a fake (it might be cubic zirconia or glass).^{[4]
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- Real diamonds are heat resistant and can withstand the radical change in temperature from the flame to the water. However, so can some black diamond substitute materials like moissanite.
- A real black diamond also won’t change color in this level of heat. If the stone starts to turn brown, then green or yellow over the heat, then it’s likely a type of moissanite.
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Sparkle test Hold the black diamond under a white light source, like a white LED or fluorescent lightbulb. If the light bounces off the diamond and you can see colored beams of light, then the diamond is real. If the reflection is dull, then it’s most likely fake.^{[5]
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- Real diamonds of any color can refract light into the different colors of the rainbow. Most will show both reflected white light (brilliance) and flashes of colored light (dispersion). There will also be a strong contrast between light and dark areas.
- Under a blacklight, a genuine black diamond will glow blue (and may show small amounts of green, yellow, red, or white, too).
- If you’re not super familiar with how diamonds refract light or don’t have a real, known diamond to compare it to, this test may not be the best way to spot a fake.

Section 2 of 5:

Real Black Diamond Qualities

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$Step 1 Many small scratches, fractures, and inclusions$

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Many small scratches, fractures, and inclusions Inclusions are small imperfections or clusters of non-diamond material that were trapped inside the diamond during its formation. Black diamonds are famous for their many inclusions—minerals such as hematite, graphite, pyrite, and others are what give black diamonds their dark, beautiful color.^{[6]
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- Black diamonds are also full of tiny scratches or fractures that turn black over time. The more fractures there are, the blacker the diamond appears.
- While some natural colorless diamonds may appear “nearly perfect” or “flawless” (free or almost free of inclusions and fractures), natural black diamonds are never “nearly perfect” and will always contain imperfections.
- Inclusions are rarely visible to the naked eye. To look for them yourself, use a jeweler’s magnifying glass with at least 10x magnification. Black diamonds without inclusions are likely fake.
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Natural black, dark brown, or dark green color While natural black diamonds look black from a distance, they may appear black or very dark brown or green (to the point of looking black) up close or from the sides. Most are opaque and have a metallic luster, although some have a translucent or “salt and pepper” appearance.^{[7]
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- Natural black diamonds (as well as lab-treated or made ones) will have a uniform color throughout. If there are any variations in color, it is likely a fake.
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Imprecise edges and cuts Because of all their inclusions, black diamonds are incredibly difficult to cut and polish with precision. If the edges of the diamond are very smooth and the cuts are clean and exact, chances are it is not a real natural black diamond (although it may be a real lab-treated or lab-made black diamond).^{[8]
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- It is possible to find a natural black diamond that’s cut precisely. However, such a gem would cost more than the typical $1,500-$3,000 per carat (or $100-$200 per carat for lab-treated diamonds).^{[9]
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Low price point Genuine black diamonds are rarely as valuable as colorless, white, or other “fancy” colored diamonds. While a high-quality, natural black diamond can cost up to $3,000 per carat, a colorless or white diamond can easily cost $5,000-$12,000 per carat. The difference in price increases with the size of the diamond—black diamonds remain around $3,000 per carat regardless of the size of the stone, while colorless or white diamond prices per carat grow as the stone gets larger.^{[10]
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- Because of the low price point, black diamonds (natural or treated) can be found in a wide variety of affordable jewelry. Black diamond engagement rings are especially popular as an alternative to classic (and expensive) diamond rings.^{[11]
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Section 3 of 5:

Types of Black Diamonds

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Black diamonds can be natural (raw), treated, or lab-made (synthetic). Raw black diamonds are self-explanatory—they’re formed by natural processes that trap deposits of graphite, hematite, and other dark minerals inside the diamond to give it its black color.^{[12]
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Research source} Other types of black diamonds are man-made:
- Treated black diamonds are often cheap white or colorless diamonds that contain many flaws or inclusions that lower their value. Other times, they begin as natural black diamonds that are gray or not dark enough to be sold. These stones are exposed to artificial heat and radiation in a lab to make their black color darker or more uniform. Most black diamonds sold for jewelry have been treated.^{[13]
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- Lab-made black diamonds are synthesized in a lab, but are chemically identical to natural diamonds. They’re then treated with heat and radiation to make them black.

Section 4 of 5:

Where do black diamonds come from?

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Most black diamonds are found in Brazil or the Central African Republic. Also called “carbonados” (the Portuguese word for “burnt”), raw or natural black diamonds are fairly rare, though not as rare as fancy yellow or pink diamonds. The first carbonados to be recognized as a form of diamonds were discovered and mined in Brazil in the 1840s.^{[14]
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- In prehistoric times, the land that is now Brazil and the Central African Republic were adjacent to each other because of the different location of Earth’s tectonic plates.
- While most diamonds are found in kimberlite deposits (coarse, igneous rock layers formed from cooled magma), black diamonds are most commonly found in alluvial deposits (material deposited by rivers or other sources of running water).^{[15]
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It’s not 100% certain how natural black diamonds formed. There are several competing and controversial theories. One suggestion is that they formed just like other diamonds in the Earth’s interior when organic carbon was compressed under extremely hot, high-pressure conditions.^{[16]
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Research source} Other theories turn to outer space—the shock of a meteorite impact may have caused them to form in the area of the crash, or an asteroid containing minerals uncommon on Earth may have deposited the material needed to make them in certain areas.^{[17]
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- Another theory suggests that the minerals needed to make black diamonds formed inside of a star relatively near to Earth, which then exploded in a supernova and distributed the minerals around the solar system.

Section 5 of 5:

Interesting Facts about Black Diamonds

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Though their dark color and rarity make black diamonds fascinating, they have a number of other properties, uses, and legends surrounding them that make them even more interesting and unique within the diamond family:^{[18]
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- Black diamonds don’t sparkle or shine like other diamonds since their dark color absorbs light. Instead, their surfaces are polished to look almost like marble.
- Black diamonds are a 10 on the Mohs Hardness Scale and are even harder than regular diamonds. Before they were used for jewelry, they were used for industrial purposes and tools like diamond-tipped drills.
- Some black diamonds are slightly magnetic and electrically conductive due to the metallic inclusions inside of them, but the effects are usually weak and uneven.^{[19]
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  Nonprofit institute responsible for gemological research and education and setting gemstone buying and selling standards
  
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- Unlike other diamonds, black diamonds come in only one color and intensity: fancy black.
- In ancient India and other cultures, black diamonds were believed to be cursed. In Italy, however, it’s believed that touching a black diamond brings good luck to your marriage.

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Tips

Purchase black diamonds from a reputable jeweler that offers a variety of high-quality black diamond jewelry to ensure you don’t buy a fake.^{[20]
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Research source} Follow their instructions for protecting and cleaning your black diamond.

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Common fake substitutes for black diamonds include black colored glass, black cubic zirconia, moissanite, and boron carbide (a type of ceramic).

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