RINGS arranged by most recent to earliest worn from its FIRST appearance starting Engagement Day.

GOLD WEDDING BAND

Made in 18K yellow gold.  It was made from Welsh gold already owned by the Royal Family.  You can read more information here: http://www.dailymail.co.uk/femail/article-1372078/Royal-wedding-Palace-confirms-Prince-William-wont-wear-ring-marries-Kate-Middleton.html

DIAMOND SAPPHIRE ENGAGEMENT RING

Prince William presented his mother's engagement ring to Miss Catherine Middleton when he proposed to her October 2010 in Kenya.  Their engagement became official on November 16, 2010.

This ring has a large oval sapphire surrounded by 14 round diamonds set in 18K white gold.  The oval sapphire is NOT 18 carats in size as reported after Kate Middleton received this ring.  It is set in 18K white gold which has been misinterpreted as an 18 carat oval sapphire.  A possible carat size (12 carats) and brief history on how Diana selected this ring can be read here: http://www.dailymail.co.uk/femail/article-1330366/Prince-Williams-engagement-ring-Kate-Middleton-sapphire-diamonds.html

More likely, the oval sapphire is at most 8-9 carats.  Based on the size of the sapphire compared to Diana's iris (the blue part of her eye which is approximately 12mm), the oval sapphire is about 13mm x 9mm and the round diamonds close to 3mm in diameter.