I don't know about the whole "vault" thing in those days. Royal ladies prior to, say, WWII had significant jewelry collections --such as Princess Helena Victoria and her sister. They would have needed lots of jet and onyx (for full mourning) in addition to amethyst (for half-mourning).
Queen Mary would have needed mourning jewels on many occasions in her grown-up life, not least of which was the death of her first fiancé. Her paternal aunts' deaths necessitated mourning, all the British royal cousins...