What does SI1+++ and D.D. mean in diamond speak?

[diamanda]

I''ve seen SI1+++, SI2++, etc... and D.D. after that. What does it all mean?!?!

 

[stone-cold11]

I think it is only USAcerted usage, not common usage, you will have to ask them.

 

[diamanda]

Gotcha. I was hoping someone might''ve asked already. I''ve sent Martin at USACerted on a hunt for a couple of rocks; I''ll be sure to ask him when I hear back. Thanks, StoneCollld!