Mineralogical and Geochemical Characteristics of Emeralds from the Bahutiya and Gurabanda Deposits of Jharkhand, India, and Comparison with Other World Emerald Occurrences

Abstract

Emerald mineralization from the Bahutiya and Gurabanda areas of Jharkhand in the eastern part of India is a recent discovery. In this deposit, emerald mineralization occurs along the contact zone between pegmatite and epidiorite-hornblende schist of the Dhanjori Group (2.1–2.9 Ga). Host rock petrographic characteristics, along with the spatial distribution of the emerald, suggest a metasomatic origin for the emerald mineralization in the study area. The well-developed emerald crystals are found along the S₂ schistosity plane, suggesting lithological and structural control on the mineralization. Electron microprobe data of the emerald indicates that the green hue is primarily due to the variable chromium content and Be could have been derived from the soda-granite of the Singhbhum Shear Zone. The average Cr₂O₃ and Cr concentration in the emerald is 0.038 wt% and 0.003 apfu, respectively. The ternary diagrams FeO–MgO–Cr₂O₃ and FeO–Cr₂O₃–V₂O₅ are plotted and superimposed on global emerald data, compiled from the literature, which shows the similarity of this deposit to other emerald deposits of the world. From the present study, it is inferred that the emerald deposits of Bahutiya and Gurabanda, Jharkhand, belong to the Type-IA category.

Keywords

Type IA emerald / metasomatism / chromium / India

RIGHTS & PERMISSIONS

2025 Geological Society of China