gems, inclusions, beryl, emerald, Brazil, Santa Terezinha de Goiás

Describes the emerald deposits of Santa Terezinha de Goiás, Brazil, presenting evidence for their stratiform occurrence and documenting the stones’ gemological properties, chemistry and inclusions. Refractive indices reach 1.593–1.602, with birefringence of 0.008–0.010, reported as the highest values then observed in emerald. Chromium and iron show the highest mean concentrations among Brazilian emeralds. Fluid inclusions are generally very small. Mineral inclusions include spinel, carbonates, mica, talc, amphibole and pyrite, with rutile, hematite, chalcopyrite, pentlandite and ilmenite also recorded.