This necklace is a sapphire, pearl and diamond necklace. It was a gift from Crown Prince Gustaf (late Gustaf V) to his wife Princess (late Queen) Victoria (née Baden) when they came home to Sweden after their wedding. Both Crown Princess and Princess Lilian has worn the necklace.
modern demi-parures of diamond & emeralds.
The necklace plus matching earrings, bracelet & brooch (the last two rarely worn) are modern, and they were a gift to the Queen by the King in the mid-eighties.
The picture of Q Silvia wearing the black pearl necklace (message number 60 on that locked thread) shows also a flower brooch. The origin and material of it was mentioned in the relatively new book of Q Silvia, if I remember correctly.
I think that the modern green stone necklace is of emeralds and forms an demi-parure with earrings.