Kate Middleton's engagement ring

Photo from here.

Prince William and Kate Middleton announced today that they are engaged.  They have been engaged about a month ago when Prince William proposed to Kate in Kenya.  The engagement ring is Princess Diana's engagement ring in 1981 with 18-karat blue sapphire surrounded with diamonds.  The Prince said the ring is special to him and so is Kate so it is just rightful for the two to be together.  The couple plans to wed in 2011.

View here the details of the royal engagement.