There are several ways to differentiate two diamonds that appear identical. For example, we can look at the optical properties, hardness, specific gravity, refractive index, and density of a diamond.

If you’re new to the world of gemstones, all these scientific terms might seem confusing. I know how much I struggled when I first started learning about the chemical compositions of diamonds. Today, we’ll talk about measuring a diamond’s density.

What Is Density?

Density is used to measure the mass of a substance per unit of volume. Simply put, density refers to the relationship between the volume of an object (how much space it takes up) and the mass itself. While density is usually used for substances, this parameter can also tell us a lot about various materials, like minerals and rocks.

We use density for many scientific purposes. For instance, measuring the density of objects can tell us whether they will float in water or sink. Another great example of different densities is vinegar and vegetable oil. You guessed it – vinegar is denser than vegetable oil, which is why oil floats on top of vinegar in your salad.

Be careful not to confuse density with specific gravity, however. Even though some use these two terms interchangeably, they’re not the same. While density estimates the “compactness” of a substance or item, specific gravity measures the ratio between density and water at 4 degrees Celsius.

How to Measure a Diamond’s Density?

Now that I’ve explained what density is, let’s discuss what it has to do with diamonds. Is density even important when it comes to estimating a diamond’s weight? The answer is yes.

No two diamonds are the same. Every naturally-occurring diamond comes with inclusions, which are microscopic bubbles, cracks, and other tiny imperfections that appear in their crystalline structure. These inclusions are the reason two diamonds with identical optical properties may have completely different densities.

A diamond’s density can vary between 3.5 to 3.53 grams per cubic centimeter or 3,500 to 3,530 kilograms per cubic meter, which is over three times denser than water. What makes diamonds so high in density is their rigid crystalline structure. Did you know that diamonds are the hardest naturally occurring substances in the world? That’s because they’re a solid form of pure carbon.

Measuring the density of other objects is done with water. However, with diamonds, heavier liquids are required. Diamonds are usually placed in a mixture of toluene and bromoform. Their density is determined after seeing whether they will float, sink, or stay suspended in the solution.

There are other ways you can estimate a diamond’s density. Most of these tests are conducted in gemological laboratories and geological institutions. Measuring diamond density is also important because it allows gemologists to differentiate authentic diamonds from fake stones.

Do Colored Diamonds Have Different Densities?

Diamond densities can differ in colored diamonds. This brings us to carbonado – a type of black diamond found in Brazil and the Central African Republic. Carbonado diamonds are the toughest forms of natural diamonds in the world. Mysterious and interesting to gemologists, their exact origin isn’t 100% certain. Some scientists even believe they come from stars. Carbonado diamonds are high-density minerals, slightly denser and tougher than monocrystalline diamonds.

There are other types of diamonds that are denser than colorless diamonds. For example, yellow diamonds mined in Africa can have a density of 3.524 grams per cubic centimeter. Other high-density diamonds include brown diamonds that were found in Brazil, which have a density of up to 3.60 grams per cubic centimeter.

Regardless of the diamond’s color, their density can be difficult to measure if they contain a lot of inclusions. Traces of imperfections can make the diamond’s density no more than useless. That’s why clean diamonds with Vvs1 and Vvs2 clarity (nearly perfect) are much more valuable. Diamonds with an IF clarity (flawless diamonds) are extremely rare and expensive.

The Densities of Other Gemstones

Gemstones have different densities. Some are low-density while others are high-density. Most gemstone densities are estimated by first measuring the weight of the gemstone in air and then placing it in water.

For example, emeralds have a density of 2.67 to 2.78 grams per cubic centimeter, while rubies have an average density of 3.97 to 4.05 grams per cubic centimeter. Similarly, the density of sapphires varies from 3.95 to 4.03 grams per cubic centimeter.

Gemstones that have the heist densities include cinnabar, with a density of 8.0 to 8.2 grams per cubic centimeter, cassiterite, which has 6.7 to 7.1 grams per cubic centimeter, and cerussite with a density of 6.46 to 6.57 grams per cubic centimeter.

Do Graphite and Diamond Have the Same Density?

Diamonds have a higher density than graphite, even though these two minerals have identical chemical compositions. But how can they have different densities? Let me explain.

Diamonds and graphite both consist of carbon, and they’re both polymorphous crystalline forms. Even though they are identical chemically, they are worlds apart when it comes to optical properties. What makes them different is their hardness. Previously, I stated that diamonds are the hardest naturally-occurring substances in the world. That’s why diamonds score 10 on the Mohs Scale, which is used to measure the hardness and scratch resistance of gemstones and minerals.

Graphite, on the other hand, has a hardness of 1 or 2 on the Mohs Scale. This makes it much softer than diamonds. To understand why graphite is less dense than diamonds, we would have to look at its chemical structure. Diamond atoms are tightly bonded, which makes them denser. As opposed to diamonds, graphite consists of carbon atoms that have a much looser, open structure.

For this reason, graphite has an average density of 2.2 grams per cubic centimeter.

Talk to an Expert

If you’re planning on buying a diamond, it’s important to do your research first. Although color, cut, clarity, and carat weight are the most important quality-determining factors, there are other properties you need to look at. A diamond’s density can determine how hard and tough it is, which is something you definitely want.

If you have any questions about the density of diamonds and other gemstones, feel free to fill out the form below. I would be happy to answer any of your questions about diamond density.

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