I remember reading from Prince Christopher of Greece (I THINK it was him), having borrowed an emerald from his mother for a costume ball. He watched in horror the stone falling to the floor, and thinking the stone would shatter, given that emeralds are brittle. Thankfully, no harm was done to the jewel.

If my recollection is correct, and the story was from Prince Christopher, he would have been referring to one of Queen Olga's famous emeralds now worn by Queen Anne-Marie.