Diamond Science Begins With Carbon and Ends in the Four Cs

It's an incredible transformation.

Unsplash / Chris Coe

When it comes to buying a diamond for the first time, there are four characteristics any prepared purchaser should consider. Called the four Cs, they are carat weight, color grade, clarity grade, and cut grade.

But a fifth C — carbon — is the best place to start when one thinks about the science of diamonds. It’s this element’s structure that makes the gem. Pure carbon also makes up another familiar item — graphite in pencils.


Admired for their stunning beauty, diamonds are also stunningly simple in composition. But the conditions needed to form them are far from simple. Made purely from carbon atoms, the birth of a diamond begins under high pressure and high temperatures, at least 2,000 degrees Fahrenheit. These conditions force carbon to form strong covalent bonds with four fellow atoms. This unit of bonds, in a shape described as tetrahedral, repeats over and over again, ultimately forming a beautiful, cubic crystalline structure we call a diamond. It’s an incredible transformation from ordinary, black pencil lead to an extraordinary, rare gemstone.

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After formation, diamonds make a dramatic entrance to the surface via volcanic eruption. Diamonds are embedded in a pipe of volcanic material called Kimberlite, where they lie, waiting to be discovered.

From volcano to gemcutter, the path a diamond takes is something important to consider. Historically, diamonds have often come from conflict regions, extracted under inhumane working conditions or sold to fund wars. Consumers can avoid these “conflict” or “blood” diamonds by purchasing stones confirmed to follow the Kimberley Process, a certification system established in 2003. Critics of the process claim it’s not rigorous enough, as it bans war diamonds but does not cover workers’ rights.

To be absolutely certain a diamond is conflict-free, consumers can stick to jewelers who commit to ethical sourcing and ask exactly where a diamond was originally sourced. Search for policies like online jeweler Blue Nile — not only do they commit to the Kimberley Process, but also address responsible mining of the stones and gold that go into their jewelry. With a team of non-commissioned diamond experts available 24/7, your buying experience will be crystal clear.


Cutting a diamond takes it from a stone covered in spidery cracks to a sparkling gem. As one of the hardest naturally occurring substances from the Earth, diamond cutters shape a diamond with another diamond, or, yes, lasers. Once cut, the GIA scale ranks stones from Excellent to Poor, assigned grades based on their ability to reflect light. This breaks down to seven factors: brightness, fire (how the light scatters into color, think Pink Floyd’s classic album color), scintillation (how it sparkles), weight ratio, durability, polish, and symmetry.

But keep in mind that the cut factor of the four Cs is different than a diamond’s shape, which refers to the overall shape, like round, princess, or marquise.


Above the other Cs, carat weight determines price. (Which isn’t the same as gold karats, which refer to purity.) A metric carat, defined as 200 milligrams, can be divided into 100 “points.” By these tiny increments, jewelers can measure diamonds very specifically. Following this system, a jeweler may call a half-carat diamond a 50-pointer. Humans like round numbers, so 0.5, 0.75, and 1.0 carat diamonds are considered magic sizes. But what’s the best kept secret to saving on a stone? Choosing something just under a magic size. Unless your eyes rival a microscope, you probably cannot tell the difference between a 0.99 carat diamond and a 1.0 carat diamond by sight alone.


Diamonds come in every color of the rainbow. Their color comes from impurities or defects that sneak into a diamond’s structure. For example, the presence of boron atoms woven into the crystal lattice gives the Hope diamond its striking blue color. Mechanical defects are considered the cause of a reddish hue, according to Smithsonian expert Jeffrey Post. There are even black diamonds, whose color comes from dense clusters of graphite, pyrite, or hematite embedded in their structure. Since these rare diamonds are opaque, their only color grade is Fancy black.

For standard, or ‘white diamonds,’ the Gemological Institute of America (GIA) measures color on a D to Z scale, D being colorless and Z being lightly colored.


The GIA sets 11 grades for clarity, from Flawless to Included. This is where the nomenclature comes in (FL means flawless, VVS1 means very, very slightly included — the categories get rather specific). To classify diamonds, jewelers look at stones under 10 times magnification to look for inclusions and blemishes. While blemishes are preventable, inclusions are not. Blemishes refer to faults on the surface which can happen from a poor polishing job or simple wear and tear. Inclusions happen before humans get anywhere close to the stones, during formation. External substances or the sheer tumult of the journey to the surface can jostle the atomic structure. Most diamonds fall somewhere in the middle.

Ultimately, no diamond is exactly the same (until scientists perfect the synthetic growing process).

Thanks to the fifth C, carbon, a combination of the four Cs creates a stone worth coveting.

Whether you are looking to build the perfect engagement ring or get the perfect jewelry gift for yourself or a special someone, Blue Nile has over 150,000 GIA-certified diamonds to choose from, giving you more choices than you could possibly imagine in any of the 4 Cs.

If you’re not shopping for something specific right now, head over to Blue Nile and enter their ongoing sweepstakes for a chance to win a $10,000 shopping spree for the piece of your dreams!

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