Grey color?

[DoctorZ]

I just compared two F color RB stones, both with VS1, excellent cut and light return with the IdealScope. Both scored around 1.5 on the HCA. Neither had any fluorescence. One was certed by AGS, one by GIA.

Against a white card, one of them appeared to be very very very slightly tinged with color, whereas the other appeared colorless. (the color differences between them were SO minute that I had to triple check and switch stone positions several times to confirm.) In the end, we decided it was a tiny but real difference.

The appraiser looked at them under the diamond light and decided that the one with the tiny bit of color actually had a bit of ''grey'' color.

3 Questions:

#1 What is ''grey'' color caused by???

#2 How does ''grey'' affect the appearance and value of the stone?

#3 Does ''grey'' come into play when color grading the stone?

 

[Smooth]

From GOG's website: "The three most common colors that diamonds decrease to are yellow, brown or gray."

I think gray color in a diamond would have pretty much the same effects on color grading, value, etc. as yellow color would.

 

[Rank Amateur]

I wonder how those colorimeters measure gray tones against the more "normal" yellow-browns when assigning a color.

 

[fire&ice]

Would the gray be a transparancy issue?

 

[DoctorZ]

So I guess the 'grey colored' F stone would have been a D or E if it had no 'grey'???

 

[Richard Sherwood]

Everything else being equal, if you can see a grey tint in one "F" stone and the other one looks colorless, take the colorless one.