How Are Colored Diamonds Formed?

Header image with fancy colore diamonds

In my colored diamond FAQ, I gave you a general overview of fancy colored diamonds, how they are graded, and which styles, cuts, and colors are most popular. In this week’s post, I will be going more in-depth about where specific diamond colors come from and how colored diamonds are formed.

Basically, a colored diamond can occur in one of two ways: if there are trace elements within the stone, and if there are certain conditions present while the diamond is being formed. Read on to discover where canary diamonds get their yellow coloration, how purple diamonds get their vibrant hue, and more.

Black Diamonds – Diamonds From Space?

The Black Orlov diamond - photo credit London Museum of Natural History
The Black Orlov diamond. Photo credit: London Museum of Natural History.

Black diamonds have been steadily gaining in popularity lately because of their offbeat look. The origins of natural black diamonds – also referred to as “carbonado” – have always been mysterious. Whereas colorless and other fancy colored diamonds are comprised of a single crystalline structure, black diamonds are polycrystalline. This just means that black diamonds are made up of countless tiny crystals, which then absorb light and create the black color.

A study performed in 2006 is responsible for creating much of the buzz that surrounds black diamonds. Researchers analyzed the hydrogen present in black diamonds, and concluded that they may have been introduced to Earth after an asteroid hit. While this has caused many people to start calling black diamonds “alien diamonds”, they don’t contain any elements that you can’t also find on Earth.

Red & Pink Diamonds

The Pink Star Diamond. Photo credit: NBC News.
The Pink Star Diamond. Photo credit: NBC News.

While hardly anyone can say they have seen and held a true red diamond, reddish and pink diamonds are created as a result of extreme heat and pressure. Fancy colored diamonds are uncommon in general, but red diamonds are the most rare. In fact, there are only 20 – 30 known to ever exist, and most of them are half carat diamonds or smaller.

To create a red or pink diamond, the diamond must form under extremely high temperatures. These temperatures then cause a defect within the growing diamond’s lattice structure, which affects the way the stone reflects light. It just so happens that this defect creates a romantic, pink glow that diamond shoppers find very desirable!

Orange & Yellow Diamonds

yellow radiant cut engagement ring

Nitrogen is the element behind the fiery, sunny colors of yellow and orange diamonds. Yellow diamonds are the most common fancy colors out there, and not just because celebrities from Heidi Klum to Carrie Underwood have been known to sport a canary diamond engagement ring.

For a yellow diamond to form, nitrogen atoms must find their way into the diamond’s structure. This nitrogen will cause the diamond to absorb blue light, thus reflecting yellow light. Faint yellow diamonds only have a few instances of nitrogen in their structure. Orange diamonds must have a very specific grouping of nitrogen atoms to get their color. Finally, the highly prized fancy intense yellow diamonds are created when there is an even distribution of nitrogen within the stone’s structure.

Green Diamonds

Radiation causes the coloration of green diamonds. Natural radiation levels in the rocks and soil where diamonds are formed will cause a green hue on a diamond’s surface. Green diamonds are extremely rare, and their green color – while completely visually striking – is not guaranteed to last forever. The radiation only forms a sort of outer green coating, rather than affecting the diamond’s color from the inside. Because their color is only surface deep, it is quite uncommon to see a vivid or intense green diamond. 

Purple & Blue Diamonds

Blue fancy diamond photo

Despite their similar coloring, purple and blue diamonds are believed to form in two different ways. In terms of purple diamonds, which are exceptionally rare, there is still some debate over how they are formed. This is the prevalent theory today: imperfections in the diamond’s crystal structure, combined with the presence of boron and hydrogen, are what cause a violet diamond.

If a loose diamond has a natural blue hue, it is because there is boron present in the diamond’s crystal structure. However, it takes quite a bit of boron and even some hydrogen to create the most vivid of blue diamonds. Most blue diamonds are a pale blue color, which is why you are much more likely to see a sapphire rather than a vivid blue diamond engagement ring.

Which fancy colored diamond is your favorite? Would you rather have a colored diamond with a delicate pale hue, or something deeper? Feel free to share your thoughts and any additional questions in the comments below!