The Brown Color Group

Brown diamonds have a tint of brownish body color. The brown group is usually less expensive than any other group due to the fact that they are less appealing to most consumers. In their lightest tones, they face up reasonably white in a yellow setting. These stones are often described as "TLB" or Top Light Brown. The brown group is graded by tone, from light to dark in much the same way as other diamonds, however their appearance may be slightly whiter than a diamond of slightly yellowish body color, in the same color grade range. Establishing the correct value with regard to significantly brown diamonds is difficult. The Argyle mines in Australia produce a significant quantity of brown diamonds, and have successfully marketed them using the descriptive names, "cognac" and "champagne".
The common shades are:
Very light brown (champagne), medium brown (champagne), Brown (dark champagne), and Dark brown (fancy cognac). A color scale has been devised by the Argyle Mines of Australia for use in grading these diamonds using C1 - C7 grades to separate them into their progressively darker tonal ranges.

In spite of the significant marketing efforts of the Argyle Mines, demand for the brown diamonds is not great and they generally command relatively low prices.