Diamond color
The color of a diamond may be affected by chemical impurities and/or structural defects in the crystal lattice.
Without any co-operative development, these early grading systems lacked standard nomenclature and consistency.
Some early grading scales were; I, II, III; A, AA, AAA; A, B, C. Numerous terms developed to describe diamonds of particular colors: golconda, river, jagers, cape, blue white, fine white, gem blue, brown, etc.
Diamonds occur in a variety of colors—steel gray, white, blue, yellow, orange, red, green, pink to purple, brown, and black.
If the nitrogen atoms are in large even-numbered aggregates they impart a yellow to brown tint (Type IaB).
About 98% of gem diamonds are type Ia, and most of these are a mixture of IaA and IaB material: these diamonds belong to the Cape series, named after the diamond-rich region formerly known as Cape Province in South Africa, whose deposits are largely Type Ia.
If the nitrogen atoms are dispersed throughout the crystal in isolated sites (not paired or grouped), they give the stone an intense yellow or occasionally brown tint (Type Ib); the rare canary diamonds belong to this type, which represents only 10% of known natural diamonds.
[4] Pink and red are caused by plastic deformation of the crystal lattice from temperature and pressure.
[7] Purple diamonds are caused by a combination of crystal lattice distortion and high hydrogen content.
[8] The majority of mined diamonds fall between white and pale yellow or brown; what is known as the normal color range.
Diamonds at the low end of the normal color range, which possess a pale yellow or brown hue, are the least desirable for jewelry.
Color is one of the four traditional factors by which a diamond is evaluated (the others being carat weight, clarity, and cut).
Refers to a grading scale for diamonds in the normal color range used by internationally recognized laboratories (GIA, IGI, & GCAL by Sarine for example).
Laboratories use a list of 27 color hues that span the full spectrum for colored gems and diamonds (Red, Orangish-Red, Reddish-Orange, Orange, Yellowish-Orange, Yellow-Orange, Orange-Yellow, Orangish-Yellow, Yellow, Greenish-Yellow, Green-Yellow, Yellow-Green, Yellowish-Green, Green, Bluish-Green, Blue-Green, Green-Blue, Greenish-Blue, Blue, Violetish-Blue, Bluish-Violet, Violet, Purple, Reddish-Purple, Red-Purple, Purple-Red, Purplish-Red).
A modifying color combination can also be added (e.g., Olive or Brown-Olive) for stones without the purest hues.
Additionally, for diamonds the following colors are used: White (which are milky), Black (which are opaque), Gray, Pink, Brown.
The terms "Champagne", "Cognac" and "Coffee" refer to different types of brown diamonds.
Diamonds that enter the Gemological Institute of America's scale are valued according to their clarity and color.
