The historical stories tell fascinating tales of changes of ownership, as the gems endure across the dying centuries. In the state crown of Britain, guarded in the Tower of London, is a stone called the Black Prince’s ruby. It belonged, when first we hear of it, in 1367, to the King of Granada. Don Pedro, King of Castille, slew him and took the gem. But Edward III of England, the monarch who established the Order of the Garter, had sent Don Pedro some 5,000 men; in thanks for these services, the triumphant Spaniard sent the ruby to Edward’s son, the Black Prince. The ruby was pierced at the top, as though it had, back in its unknown past, been part of a fabulous necklace of an Orient potentate; today, the hole is filled with a small ruby set in gold. The Black Prince, dying before his father, left the stone to his son, who became King Richard II in 1377 and was deposed by Henry IV in 1399 and probably murdered in the very Tower where the ruby now rests. Henry V, to whom it came in his turn, wore the stone at the Battle of Agincourt, where against great odds he defeated the French. After that, it was deemed safer to leave the gem in London; there it became part of the crown jewels. But the crown jewels were scattered by the Puritans in 1642, after Cromwell became Lord Protector. With the Restoration, the Black Prince’s ruby was returned to the crown and has remained unharmed since—save that modern methods of examination have revealed that it is not a ruby at all, only a “balas ruby,” that is, a spinel. _Other Precious Stones_ The Stuart sapphire, a great oval an inch and a half by an inch with a hole near the top, can be removed from the royal crown and used as a pendant. This sapphire, after James II was deposed by the Bloodless Revolution of 1688, was carried away from England by the Young Pretender, who—when he grew older and more sage—bequeathed the sapphire, along with other Stuart relics, to George III of England. Since then, it has rested quietly in the crown. Other precious stones have had their historic moments or movements. Catherine the Great of Russia sent thousands of workers into the Ural mines to hunt for amethysts. Some of Napoleon’s gifts to the Empress Josephine were of emeralds and pearls. The American Museum of Natural History holds among its treasures a great star sapphire weighing 563 carats. _The Crystal Palace_