A needle is a thin, elongated crystal inclusion that looks like a tiny rod at 10x.
In more detail
In corundum, needles are often rutile; crossing groups of them are called silk. In moissanite, GIA found thin white needles, roughly parallel, running down from the table along the optic axis. That pattern is a hint toward moissanite, not proof.
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
- Crystal: A crystal is a mineral crystal contained in a diamond.
- Silk: Silk is a mass of fine, crossing needle inclusions, usually rutile, in ruby and sapphire.
- Moissanite: Moissanite is silicon carbide, one silicon atom for every carbon atom, in a hexagonal crystal. It is a diamond simulant, and every moissanite in jewelry is laboratory-grown.
- Inclusion: An inclusion is a clarity characteristic inside a diamond, or one that reaches the surface from inside.