Aventurescence

aventurescence \ə-ˌven-chər-ˈe-sən(t)s\ noun: an optical reflectance effect in certain gems in which a metallic glitter arises from minute mineral platelets within the material

Etymology: Italian a ventura by chance (referring to the chance discovery of aventurine glass in the 18th century)

Have you seen Michelangelo Antonioni’s L’avventura, by any chance? It is not about aventurescence.