My reading is that it is a type IIa diamond which indications suggest is a fragment of a much larger diamond. They can tell whether a diamond is a type IIa or not in the lab. Im sure the diamond was marketed as such or else I would imagine it wouldn't have raised the amazing amount it did. What is in question as I understand is whether it is a fragment of a much larger diamond. If it is a fragment then we could easily be looking at $5m dollars or so for the whole of that stone alone!
Im not a diamond expert so I could be wrong on determining a diamond type and so will stand corrected.