The Fascinating Formation of Colored Diamonds and the Color Origins of Lab-Grown Diamonds

Today, jewelry counters are dazzling with a wide range of diamond pieces. Alongside the traditional favorite white diamonds, a growing variety of colored diamonds have emerged. As people’s preferences shift, colored diamonds have gained increasing popularity. But how are these diamonds, from white to pink, blue, green, brown, and red, formed?

In this article, we’ll discuss how the colors of natural diamonds and the increasingly popular lab-grown diamonds come about.

White Diamonds

White diamonds are the most common and form the essential color spectrum in diamond grading. From the colorless D grade to the Z grade (which is a faint yellow or brown), the variation mainly results from the presence of nitrogen. A D-grade diamond typically contains little to no nitrogen. In colorless diamonds, a slight yellowish tint is the primary factor contributing to a lower grade.

Yellow Diamonds

Yellow diamonds are often the result of nitrogen elements. Nitrogen atoms replace some of the carbon atoms in the diamond's crystal structure (about 100 nitrogen atoms for every million carbon atoms). As the diamond forms, it absorbs parts of the red and blue-green light, giving the diamond its yellow hue.

Blue Diamonds

Blue diamonds are caused by the presence of boron. The boron atom has fewer electrons in its outer shell than carbon, creating vacancies in the diamond’s covalent bonds. These vacancies allow other electrons to fill the gaps, causing the red portion of the visible light spectrum to be absorbed, and leaving behind blue light. Blue diamonds are extremely rare, and most tend to have a grayish tint.

Red and Pink Diamonds

The formation of red and pink diamonds is somewhat unique. Unlike other colored diamonds, they lack specific chromophores responsible for their color. It is theorized that the color comes from lattice distortion caused by plastic deformation. When diamonds are formed under high-pressure geological conditions, internal structural changes occur, creating new energy levels that absorb certain light wavelengths, producing red or pink hues. Red and pink diamonds are particularly rare.

Green Diamonds

Green diamonds form due to natural radiation from the Earth’s natural radioactive particles, which alter the diamond’s crystal structure. These diamonds typically have a thin green layer on the surface, which can be lost when the diamond is polished. Therefore, naturally irradiated green diamonds are exceedingly rare, with most green diamonds being treated artificially to achieve their color.

With technological advancements, the colors of lab-grown diamonds are becoming more diverse. Unlike natural diamonds, the colors of lab-grown diamonds are typically influenced by the following methods:

Additives:
While diamonds are composed primarily of carbon, other elements are added during the synthesis process to replace carbon atoms in the diamond lattice. For example, nitrogen is prevalent in the atmosphere, so diamonds created using the high-pressure high-temperature method often display yellowish or brown hues. If metal elements are added, they can reduce brown hues and produce pleasant light yellow or golden diamonds. Additionally, the addition of boron can result in blue diamonds.

Pressure Effects:
During the high-pressure high-temperature synthesis, pressure causes plastic deformation in the crystal structure, creating defects that produce 'color centers.' This results in diamonds displaying colors like brown, pink, or red. In CVD-grown diamonds, stress within the crystal can also cause plastic deformation, giving rise to brownish hues.

Radiation and Heat Treatment:
Diamonds of lower quality with more impurities or undesirable colors can be artificially treated to alter their color. By exposing these diamonds to radiation, their crystal structure is altered, creating vacancies or displacements that produce colors such as green, blue, or deep blue. These diamonds can then undergo heat treatment to achieve colors like yellow, pink, or red.

Surface Treatment:
Surface treatments are primarily used to improve diamonds with yellowish hues. One such treatment involves coating the diamond’s girdle with a blue substance to improve its color. Another involves applying a thin layer of colored oxide on the diamond’s surface to conceal undesirable hues. Chemical vapor deposition (CVD) is another method in which a diamond film is grown on the surface of the diamond to improve its color.

The unique allure of colored diamonds stems from their extreme rarity and rich, vivid hues – the rarer and more intense the color, the higher their value. Precisely for this scarcity, colored diamonds have become a highly sought-after choice in investment and collection. With the continuous advancement of lab-grown diamond technology, colored lab-grown diamonds boast an even more diverse color spectrum, bringing abundant personalized options for consumers. Specializing in the lab-grown diamond sector, Foshan High Light Intelligence Technology Co., Ltd. owns an extensive inventory of colored lab-grown diamonds. We offer a full carat range from 0.5 to 15 carats, covering the complete color grades from Light to Fancy Vivid, with a wide selection of hues available. Our comprehensive supply fully meets the diverse needs of various designs, wear, investment and collection scenarios.