Gemmological Characteristic of "Tanghe Jade"

The gemmological characteristics of "Tanghe jade" were studied by means of microscopic observation and infrared spectroscopy. The testing results showed that the main mineral component of "Tanghe jade" is tremolite and its gemmological characteristic is similar to that of nephrite. The tremolite grains in "Tanghe jade" are small and it contains metasomatic residual carbonate phenocrysts, which are fiber-interwoven structure with disorderly arrangement and insufficient luster. "Tanghe jade" is mostly glass luster, and the common grass-shape feature("shuicaohua") is caused by impurity minerals. The overall quality of "Tanghe jade" is similar to nephrites from Korea, and Jiangsu, Guangxi and Guizhou Province of China. As for "Tanghe jade" pebble, it has a bright-coloured skin and a high craft value and utilization prospect. Comparing the deposit characteristics, mineral components, geological structure, and gemmological characteristics of "Tanghe jade" with the nephrite from other origins, the gemmological name and market position were clarified. When the content of tremolite is above 95%, it can be called nephrite.When the content of tremolite is between 90%~95% and the carbonate mineral in "Tanghe jade" is more than 5%, it should be called as "tremolitization marble" or "tremolite jade (carbonate minerals/calcite/dolomite)".