Causes of colour in heat treated brown diamonds and synthetic brown diamonds are similar to treated pink diamonds.
In natural diamond the colour is related to a lattice imperfection. This can be mimicked in synthetic or treated diamond by a variety of treatments including annealing, heating or irradiating. The heat and pressure or irradiation can result in the lattice deviation resulting in the brown or pink colour.
Synthetic brown diamond is created by compressing graphite under extreme pressure and heat to above 1500 Celsius. The treatments were perfected in several laboratories in Russia, United States and China.
Lazare Kaplan Internationals Belgium subsidiary Pegasus Overseas Ltd marketed the General Electric processed diamonds under the name GE POL or in the USA as Bellataire.
This led to a technique for creating, or treating brown diamonds into higher valued colours like yellow or colourless diamond.
The disclosure of the treatment is noted by the “GEPOL" inscribed on the girdles of every treated diamond.
Brown diamonds are often marketed with expensive sounding names like Cognac, Champagne or Chocolate diamonds. Natural brown diamonds are a cheap alternative to more expensive colours.