I was asked to ascertain the validity of a ring with 'three white' stones. I came to the final conclusion that these three stones were not even 'lower-grade' cubic zirconias.
As I am not a "Certified Diamond Appraiser" (my experience with similar stones) spans well over half a century. The reasons were many as each stone was carefully examined using my 500x power digital microscope.
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1) The very first 'indication of problems' was that the centre stone was transparent through the "Pavilion" facets.
2) The girdle of the centre stone was too 'thick and unpolished'.
3) There was an uneven edge on the rim of the Girdle.
4) The "Crown Facets" were not polished evenly and did not meet the "Girdle".
5) The 'yellow plating' was not uniform underneath the basket of the claws.
7) It's very easy to see that the 'Girdles' of the shoulder stones are also very thick.
8) No 'genuine stones' would be created like the stones in this ring. 
9) The 'pre-polishing' of this ring left little to guess where this ring was made? BTW, this shoulder stone on the right was set crooked.
