A grain center is a small, concentrated area of crystal distortion inside a diamond. It can be white or dark and can look like a thread or a pinpoint.
In more detail
It comes from distortion in the crystal, not from a foreign mineral. GIA counts it as an inclusion.
On a grading report
Drawn in red on the clarity plot of a full GIA report and named in the key to symbols. A Dossier has no plot but can name it in its list of up to four.
Related terms
- Internal graining: Internal graining is lines, angles or curves inside a diamond caused by irregular crystal growth. At 10x they can look whitish, colored or reflective, or lower the transparency.
- Pinpoint: A pinpoint is a very small crystal inside a diamond that looks like a tiny dot at 10x.
- Inclusion: An inclusion is a clarity characteristic inside a diamond, or one that reaches the surface from inside.