Mineral Composition and Chemical Composition Characteristics of Green Nephrite from Three Origins

Abstract:

The mineral and chemical compositions of green nephrite samples from Qiemo County， Xinjiang Uygur Autonomous Region， Hualien County， Taiwan， China， and British Columbia， Canada were systematically analyzed by gemological tests， microscope observation， electron probe X-ray microanalyser（EPMA）， and laser ablation microprobe inductively coupled plasma mass spectrometry（LA- ICP- MS） analysis. The results show that the green nephrite from the three origins are mostly green-dark green， containing spotted or banded black accessory minerals， whose gemological features are similar and difficult to distinguish. Under the microscope， it can be seen that the main mineral composition of green nephrite samples from the three different origins are tremolite， but that from Canada can contains a small amount of actinolite and pyroxene. The Qiemo green nephrite is calcium-chromium garnet， and the Canada and Hualien green nephrites are grossularite. The results of EPMA show that the main mineral of the samples are tremolite， and the color of green nephrite changes from light to dark with the increase of Fe and Cr content. The results of LA-ICP-MS show that the content of Sc in the Hualien green nephrite is significantly higher than that in the other two origins， which could be regarded as the typomorphic characteristics of the chemical composition of the Hualian green nephrite.