Loose Diamond :

The Centenary diamond, being a D-color diamond is a Type IIa diamond, free of nitrogen and all other chemical impurities. They are also structurally perfect diamonds, without any plastic distortions. Thus factors that usually cause color in diamonds are absent, and therefore these diamonds are absolutely colorless. The diamonds are said to be chemically pure and structurally prefect. However, they constitute only about 1-2 % of all naturally occurring diamonds.