I also think it is a beautiful brooch Beth but I haven`t heard anything about its history except that Camilla, DoC has other aquamarines, that may be part of a set? She could have had them from her family? I know the aquamarine, as the 3 row pearl choker clasp is definitely a jewel she had from her family. These pictures were at the theatre on 25th Feb 2010, there is also a bracelet visible in full length photo. At St Pauls Cathedral in 2008 :