Study on Colour and Gemmological Characteristics of Viridis Nephrite from Qinghai Province

Nephrite presents in many differernt colours and the viridis nephrite occurred in Sanchahe East Kunlun is very popular in the market.In order to study the main components and colouring causes of viridis nephrite,the authors select some typical samples with gradual changing colours and test them with infrared spectrometer,Raman spectrometer,ICP-MS and USB2000 fiber optic spectrometer.The infrared spectrum and Raman spectrum indicate that the major mineral in viridis nephrite is tremolite.The results from ICP-MS show that the intensity of colour is proportional to the quantity of Cr³⁺.USB2000 fiber optic spectrometer shows that the main wavelength of viridis nephrite is 557 nm and the spectrum of orange area and blue purple area were absorbed.Based on a series of experiments,the authors also discussed the position of Cr³⁺ which caused the changes of colours in viridis nephrite.And Cr³⁺ was found in basic magma rock.