taaffeite, Sri Lanka, gems

Gübelin describes “taprobanite,” a rare red gemstone from Sri Lanka initially thought to be taaffeite because of its similar appearance and gemological properties. Detailed examination showed it to represent a distinct member of the taaffeite mineral group, characterized by differences in chemical composition, crystallographic properties, and optical behavior. The study discusses its identification, physical and optical constants, absorption characteristics, inclusions, and relationship to taaffeite, emphasizing the difficulty of recognizing such rare stones by conventional gemological testing alone. The name derives from Taprobane, the ancient name for Sri Lanka.