The Art of Creating Colored Diamonds: Techniques and Methods

The glittering classic colorless diamond is the most well-known diamond variety, but diamonds come in a variety of colors including blue, green, pink, brown, black, and more.

What Are Colored Diamonds?

Colored diamonds (also called fancy diamonds) are diamonds that have a noticeable body color when viewed in the face-up position. Brown and yellow are the most common colors in natural colored diamonds. Diamonds with natural pink, blue, orange, green, red, and violet colors are extremely rare.

The popularity of colored diamonds has increased in recent years, and more engagement rings are featuring colored gemstones, like fancy diamonds. When choosing a colored diamond, its hue is an important quality factor. GIA uses a different grading scale for colored diamonds that evaluates how light and dark the stone is as well as the color intensity.

Natural Formation of Colored Diamonds

When foreign particles are trapped during the crystallization process when diamonds are formed, it alters the chemical process and changes the outcome. The result is a beautiful, rare, and exceptional diamond in a unique coloring. In order to produce a particular hue, thousands of variables must be present in just the right amounts, at just the right times. Here are some of the causes for colored diamonds:

• Blue: A tiny amount of boron creates a blue diamond. However, these are extremely rare.
• Green: A natural green diamond develops at the end of their journey to the earth’s surface. The color comes from natural irradiation that is typically caused by alpha particles. This is usually confined to a very thin layer on the diamond rough’s surface so it’s rare that diamond has green throughout.
• Purple: The presence of hydrogen creates purple and violet diamonds.
• Yellow or Orange: nitrogen in the right amounts will produce orange or yellow diamonds. The amount of color depends on the amount of nitrogen within the diamond’s crystal structure.
• Pink and Red: Scientists are unclear about how pink and red diamonds are formed. They think the color is caused by plastic deformation as a response to extreme natural stresses deep below the surface of the earth. This means that they don’t start their growth process pink, making pink and red diamonds extremely rare.
• Brown: More amounts of nitrogen or defects within the diamond lattice will create brown diamonds.
• Black: Black diamonds don’t get their “color” from a substance during their formation. Instead, the black you see is from all of the dark inclusions that block light from passing through them. This gives the stone a dark appearance. Common inclusions in black diamonds include graphite, pyrite, or hematite.

Pros and Cons

An engagement ring featuring a glittering heart diamond is a grand romantic gesture. This type of cut is rare, unique, and eye-catching. Heart-shaped diamonds typically cost 15 to 20 percent less than round cuts. However, it’s a less common cut (especially in bigger carat weights) and every heart looks different. Some are taller while others are wider depending on their symmetry and quality, so you’ll need to carefully look at each heart diamond that you’re considering. In order to get a distinct heart shape, it’s recommended that you select a one carat weight or more.

• HPHT: This method utilizes a diamond “seed” that’s added to carbon. The diamond seed is a small, natural diamond fragment that undergoes extreme temperature and pressure conditions. In fact, the diamond seed and carbon’s extreme temperatures are in excess of 1,300 to 1,600 degrees celsius and pressures of one million pounds per square inch. These extremes replicate the heat and pressure conditions deep within the earth where natural diamonds form. Then, carbon forms around the diamond seed and is then cooled.
• CVD: This process is a chemical vapor deposition system that begins with a diamond “seed.” The seed impacts the resulting lab diamond, so it’s important to select the strongest and highest grade natural diamond piece in terms of color and clarity. During the CVD process, the diamond seed gets placed in a vacuum chamber and it’s filled with gasses that are heavy in carbon. It’s then heated to over 1,000 degrees, which turns the gasses into “plasma.” This plasma helps “build” the layers of the lab diamonds.

When colored diamonds are produced, a gas mixture is added to the CVD reactor and then additional treatments are used toward the end of the process. Some of these include:

• Irradiation method: This is a process that changes the color of the diamonds through high-energy electron saturation.
• Diffusion method: In this process, certain elements are introduced into the atomic lattice of a gemstone during heat treatment to change or accentuate its color.

Natural Diamond Color Treatments

Like lab-made diamonds, natural diamonds can get treatments to enhance or change their color. Exposing natural diamonds to irradiation changes some diamond’s color. For example, heating irradiated diamonds to above 1000o C changes most blue-to-green colors to brownish or orangey yellow, greenish yellow to yellow, or pink to red.

Similarly, annealing is a controlled heating and cooling process that is used after irradiation to adjust a diamond’s color. Unlike HPHT, the temperatures reached are generally lower, and high pressure is not required. It’s typically used to change diamond color to brown, orange, yellow, pink, red, and purple. The resulting color after treatment is due to the beginning material and the defects in the gemstone. In general, annealed diamonds are stable for jewelry repairs.

HPHT is a method of annealing at high temperature and high pressure. The HPHT reactor can be used both to grow laboratory-grown diamonds and to change the color of natural or CVD laboratory-grown diamonds. This process can make colorless, pink, blue, green, yellowish green, or yellow diamonds. HPHT annealing is often used to lighten the color of some brown diamonds. This form of diamond treatment is stable, permanent, and difficult to detect except by a well-equipped grading laboratory.

Factors Influencing the Value of Colored Diamonds

As noted previously, diamonds with natural pink, blue, orange, green, red, and violet colors are extremely rare. When choosing a colored diamond, its hue and intensity are important. Look for color banding, inconsistent color, and pale colors. Some natural diamonds don’t come in larger carats, so keep this in mind when selecting a colored diamond.

GIA uses a different grading scale for colored diamonds that evaluates how light and dark the stone is as well as the color intensity. GIA grades colored diamonds by describing color in terms of hue, tone and saturation. Their reports for colored diamonds are different from the versions for colorless diamonds.

Colored diamonds’ popularity will continue to grow. The process to create lab-made diamonds continues to improve as well. When selecting either a natural or lab-made color diamond, carefully evaluate the color for its hue and intensity. Colored diamonds are beautiful and exquisite, and if it’s a natural diamond, it’s incredibly rare.