There might have been the grandest of occasions when the thing was slung around a neck! But I would expect that it was attached at the shoulders to appear more like a collar of an order.
--Previous Message-- : Royal-Magazin calls the ornament both a devant : de corsage and a necklace. The history : given there: : : : http://www.royal-magazin.de/england/mary-lascelles-harewood/mary-imperial-sapphire-necklace.htm : : Sartorial Splendor says only that it was an : ornament given to the Princess by her : husband. Perhaps in the Russian court this : could have been worn as a necklace, but it : does seem very large. :