Natural Brown Diamonds-

Why Are They Brown?

The term Cognac diamond has been used to describe natural dark brown diamonds. A diamond can occur in nearly any color, though colorless (white), yellow and brown are by far the most common.

Colored diamonds contain impurities or structural defects that cause the coloration. The most common impurity, nitrogen, causes a slight to intense yellow coloration depending upon the type and concentration of nitrogen present. Brown or Cognac “amber” diamond crystals show some deformation called “brown graining”. They also contain nitrogen atoms.

A brown diamond also receives a large part of its unique color from the light that was absorbed through structural defects in the stone's crystal lattice.

Tones Defined

Natural fancy brown diamonds are assessed according to intensity of color, or a combination of saturation and tone. Tone refers to the lightness or darkness of a brown diamond, and the continuum in between.

The following terms are used loosely to describe the intensity and purity of the brown tone in polished diamonds;

Top Light Brown
Medium Brown (champagne)
Brown (dark champagne)
Dark Brown (cognac)

Stuller also carries top light brown (TLB), which refers to a very light shade of brown stones. On the diamond color scale, these diamonds would be compared to L-M color. In the figure above, these diamonds are displayed as C1-C3.

Origin

North of Western Australia

Most of the pink and brown diamonds come from Argyle Diamond Mines located in the East Kimberley region in the remote north of Western Australia. Argyle is one of the largest diamond producer in the world by volume, although due to the low proportion of gem-quality diamonds, is not the leader by value.

It is the only known significant source of pink diamonds, producing over 90% of the world's supply. It additionally provides a large proportion of other naturally colored diamonds, including champagne, cognac and rare blue diamonds.

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