Pearls are enjoying something of a renaissance. The #VivienneWestwoodNecklace hashtag on TikTok has 31 million views – mostly breathless unboxings of the British designer's now cult pearl-and-spaceship pendant necklace. Then there are celebrities like Harry Styles and Hailey Bieber who have been showing off their fondness for pearl necklaces, and the growing popularity of social media "aesthetics" such as #OldMoney...