I do not know for Queen Maxima's earrings. The Dutch jewellery pieces are so versatile that it is very easy to get confused and lost...
The diamond pendant suspended from Empress Michiko's diamond riviere is not a single large diamond, but a diamond cluster. We can see it on these pictures (taken on 23 May 2007 at Uppsala Castle during the Emperor and Empress' State Visit to Sweden):
The pendant is removable (Empress Michiko has worn her diamond riviere both with and without the diamond pendant).