black spot in diamond

Hi Diamond Guy,

My fiance recently proposed to me with a ring bought from Blue Nile. It is a round brilliant in a solitaire setting. The diamond came with a GIA certificate which was graded G color VS2 clarity, excellent/ideal cut. After wearing the diamond for a few days I noticed a black spot right in the center of the diamond (which was only visible when holding the ring straight up in front of me). I went and had it appraised and the appraiser told me it was a small carbon spot in the back of diamond. The GIA plot on this diamond had a small feather in the center of the table and we thought this could have been it.

I returned the diamond for another of the same specifications. I thought I was safe with the new one because the GIA plot shows no flaws in the middle of the diamond and only around the perimeter. Sure enough, when I received this diamond, I found the same black spot in the same place as the last one.

My question now is (assuming this diamond is actually a new diamond, which I do trust Blue Nile that it is), is it possible this black spot is not carbon and is actually a reflection of the setting below? Or is it simply the way the diamond reflects light? Blue Nile says they will look at it for me but I do not want to send it back and not have it for another two weeks.

Thank you for your input,
Gina

P.S. Neither of these diamonds have a cutlet, which I hear can cause a black spot in the back of the diamond as well.