The Green Spots in Nephrite—Grossularite

Abstract

Recently, a variety of nephrite with emerald green spots appeared in the nephrite market. There is no report on the mineral composition and green spots for this type of nephrite. Under a higher magnification optical microscope, the complete crystal shape, microstructure and the distribution of the green spots in nephrite were observed. The chemical compositions and mineral phases have been identified using Raman scattering spectrometer and Energy-Dispersive X-ray Fluorescence Spectrometer (ED-XRF) techniques. It was found that the main mineral composition of nephrite is tremolite and the green spots are grossularite. The main coloring element in grossularite is Cr. Therefore, the Cr-bearing grossularite is the main reason for the green spots occurring in the nephrite. It differs from the colouration of traditional green nephrite (jasper) and Qinghai CuiqingYu. The green garnets usually have been observed in jasper, and never found previously in other varieties of nephrite. A certain number of green grossularites with crystal shapes in the nephrite is very important for the study on the origin of this nephrite deposit and the place of its origin.

Keywords

• nephrite
• grossularite
• tremolite
• green spot