The diamond industry, BGM stands for Brown, Green, or Milky – terms that describe undesirable undertones or characteristics in a diamond that can affect its appearance and value:

•Brown: A subtle to strong brown tint that can make the diamond look less bright or lively.

•Green: A greenish hue, often caused by natural radiation. It can be faint or more prominent and may not be uniformly visible.

•Milky: A cloudy or hazy appearance caused by internal graining or structural irregularities, which can reduce the diamond’s brilliance.

These features might not always be noted on standard grading reports (like those from GIA), so high-end dealers and buyers often check for BGM separately when assessing a diamond’s true visual quality.