Very attractive fancy purplish pink diamond ring, 1930s. Sold 1,561,000 CHF at Sotheby's Geneva, 14 Nov 2007, lot 356.

The fancy purplish pink Asscher-cut diamond weighing 6.54 carats, set between triangular diamond shoulders, size 52.

Accompanied by GIA report no. 15644798 stating that the diamond is Fancy Purplish Pink, Natural Colour, VS2 Clarity.

Further accompanied by GIA Diamond Type Classification report stating: 'Scientists classify diamonds into two main "types" - type I and type II - based on the presence or absence of nitrogen which can replace carbon atoms in a diamond's atomic structure. These two diamond types can be distinguished on the basis of differences in their chemical and physical properties. Type II diamonds contain little if any nitrogen and they are subdivided into two groups (IIa and IIb) both of which are quite rare (less than 2 % of all gem diamonds). 

According to the records if GIA Laboratory, the 6.54 carat cut-cornered rectangular step-cut diamond described in the GIA Colored Diamond Grading Report # 15644798 has been determined to be a type IIa diamond. Type IIa diamonds are the most chemically pure type of diamond and often have exceptional optical transparency. Type IIa diamonds were first identified as originating from India (particularly from the Golconda region) but have since been discovered in all major diamond producing regions of the world. 

Among famous gem diamonds, the 530.20 Cullinan and the 105.60 Koh-i-noor are examples of type IIa.'