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

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 epidioritehornblende 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.