David,

I saw this diamond, BLOOOO  , of course, and in the description it mentioned that it had a Type II classification from GIA.  I tried to zoom it and read what it said, but it was too blurry.  I can tell that it has more nitrogen atoms and less carbon atoms than the normal diamond, but can you either point me to a legible copy of the document or give the straight poop in plain English, please? 

thanks!

That's interesting.  I get the feeling that this is a naturally irradiated puppy.  At 1.04 ct, the price is in excess of 100k.  Plus the GIA cert claims it for Natural Fancy Dark Bluish-Grey.  Not my favorite blooo, but if it were free.....

A type II diamond is a diamond with little nitrogen trapped in the carbon lattice. This is then further split into type IIa (where no further impurities are present, but the crystal lattice may be deformed giving rise to brown, red or pink colour) and type IIb where boron atoms are diffused in the carbon lattice, giving rise to a blue or blue-gray colour (probably as in the case above). Nothing to do with radiation.

Type II diamonds are relatively easily distinguished from type I (with relatively large amounts of nitrogen in the lattice) through infrared spectroscopy and fluorescence/UV reaction. There is a hypothesis (or myth?) that Golconda diamonds are type II diamonds, hence their high colour due to almost total lack of nitrogen. Unfortunately, however romantic, this is difficult to verify since a Golconda provenance is quite hard to prove (the only way to be absolutely sure is to trace the diamond to a date prior to 1725 or all the way back to the mine).

Note that many synthetic diamonds (particularly those grown through the CVD method) are effectively type IIa diamond; also if a coloured type IIa diamond is subjected to high temperature/high pressure treatment, the lattice will "relax" back into its normal shape, and the diamond will lose much or all of its body colour; not a smart idea if it's red or pink, but perhaps with some dark brown... (the treatment can be detected with high reliability).