Diamond color can be determined by nature or a laboratory. The Gemological Institute of America (GIA) reports that only 1 in 10,000 diamonds is a natural colored diamond, outside of the standard D-to-Z color-grading scale. Natural colored diamonds are found in just about every hue of the rainbow. There are 27 different shades of diamond colors listed by the GIA.
Natural Colored Diamonds
Every carat requires billions of atoms to bond together. To create a colorless stone, each atom must be carbon. The slightest addition will result in a diamond color. A dash of boron will create a blue diamond; yellow diamonds contain nitrogen; radiation from surrounding rocks capture electrons that spawn a green color; red or pink hues develop due to shifts in the electron structure as it travels to the diamond surface.
Lab-Created Diamond Colors
Natural diamond colors can be mimicked in a laboratory. Color treatments are performed to enhance diamond tints. A pale-yellow diamond treated with a thin layer of blue will give the illusion of a higher color grade. Irradiation can be used to make a diamond appear more green, blue, yellow, pink, red, or brown.
Diamond color grades issued by the GIA describe the hues of fancy stones in three ways: hue (spectral colors), tone (lightness and darkness) and saturation (neutral to vivid). Pressure and radiation can intensify the diamond color naturally.
Common Diamond Colors
- Red Diamonds: The rarest and most expensive natural colored diamond.
- Orange Diamonds: Nitrogen is said to be the element that modifies the color of orange diamonds.
- Yellow Diamonds: A very common diamond color, mined mainly in South Africa, vivid yellow stones are often enhanced with blue treatment to make the diamonds appear colorless.
- Green Diamonds: Fewer than ten natural colored green diamonds come to market every year.
- Blue Diamonds: When the element boron is present in a diamond, the nitrogen level is very low, and the stone takes on a blue hue. Some natural blue diamonds have high hydrogen concentrations or contain nickel.
- Purple Diamonds: Second to red as the rarest, natural purple colored diamonds account for one percent of all diamonds mined in Mir Kimberlite Siberia, where these fine treasures are recovered most.
- Pink Diamonds: Ninety percent of all natural colored pink diamonds come from Northwestern Australia, although the pink gems can also be found in India, Brazil, and Tanzania.
- Brown or Chocolate Diamonds: Defects in the diamond structure absorb light and result in the brown color. Nitrogen also contributes to the chocolate hue. Champagne diamonds, cognac diamonds, and chocolate diamonds are all variations, termed by the richness of the brown tint.