Pearls and Perlmutt[AN: AKA 'nacre' or 'mother of pearl'] are made by organic beings.
Aliens have never seen this Product before coming to Earth.
Of course, Earth has a new high-selling Export product. -- Anon Guest
Calcium carbonate is nothing new. It's formed from two relatively common elements in the periodic table and simple life forms make it the Universe over. Only one planet has evolved lifeforms that uses it in a laminal form. Aragonite, formed in plates, refracts light in intriguing ways. Many species find ways to create it -or something like it- in laboratories.
Only Earth has creatures that make it naturally.
Trade in cultured pearls skyrocketed almost overnight. All it took was one paua shell pendant and Earth had the Galactic Alliance's undivided attention. As a novelty, it was fascinating. Nacre made by organic beings. Further, other organic beings had figured out how to farm it before they figured out how to create it.