The Nature of Brown Diamonds
Brown diamond is the most conventional color variety of natural diamonds. In the past, the brown color makes it unexceptional as gemstones and in fact most are used for industrial purposes. However, due to technical advances and improved marketing programs, especially in Australia – where most brown diamonds came from, brown diamonds are now valued comparable to gemstones. Australian diamonds constitute one third of the world production and are especially rich in brown stones. Western Australia’s Argyle Diamond Mine is the world’s largest producer of these stones.
To understand the origin of the brown color, large amount of scientific research was spent. From the scientific researches that were conducted, several causes have been identified. Causes include irradiation treatment, nickel impurities and lattice defects associated with plastic deformation, wherein the latter are considered as the predominant cause, especially in pure diamonds.
Irradiation treatments entail revealing the stone to electromagnetic rays (ionizing radiation) or gamma rays (cobalt 60 radiation) to discharge electrons from their normal location, moving them to more desirable color-producing locations. Neutrons will be utilized in the irradiation process, whether it would depend on the mineral to be treated, and the desired color adjustment, alpha particles, beta particles, electrons, gamma particles.
Laser-drilled diamonds can also be a factor on the origin of this stone. The laser-drilling of diamonds to decrease or eliminate foreign crystal inclusions, or iron-oxide stained fractures, has been performed for over 20 years. Drilling is achieved using an infrared laser to bore microscopic holes into a diamond, creating an access channel to the inclusion.
A high-pressure high-temperature treatment has been intended to heal lattice abnormalities and alter brown diamonds into yellow or even colorless stones.
High-Pressure (70,000 atmospheres) High-Temperature (2,000º C) treatment or HTHP was developed by General Electric in 1999, to reduce or totally get rid of a brownish hue in some Type IIa diamonds. Type I diamonds have nitrogen impurities that captivating some of the blue light spectrum, thereby making the diamond come out yellow, while Type II diamonds have structural imperfection known as plastic deformations created during crystal development, that can cause a brownish color. High-Temperature High-Pressure treatment can in some cases ‘restore’ these deformations, whitening the diamond’s appearance.
There is nothing intrinsically incorrect with gem enhancements as long as you are made aware of their use. New treatments are being made available all the time, and gemological testing centers are constantly changing and modernizing their testing regimes to prevent the unidentified enhancement that can slip through the cracks.
Either way, brown diamonds are the new classic ranging from the subtly elegant champagnes to the smooth, rich cognacs.