Gray???

[headlight]

PS Friends,
My cousin came to me asking why the backside of a diamond pendant is gray (he diamonds, not the mounting).
Any ideas of what it could be?
Thanks!

 

[Karl_K]

Oil/lotions/gunk
Professional steam clean and check again.

 

[Garry H (Cut Nut)]

PS Friends,
My cousin came to me asking why the backside of a diamond pendant is gray (he diamonds, not the mounting).
Any ideas of what it could be?
Thanks!

Take a good photo with a good phone in good light