Mineral Components and Identification of Laos Stones

Recently a large number of Laos stones from Laos has appeared and impacted on the larderite market in Fuzhou.Several samples of Laos stones were collected in the Fuzhou market and were analyzed by X-ray powder diffraction (XRD),mid-infrared spectroscope(MIR)and near-infrared spectroscope(NIR).The study result shows that Laos stones have the relative densities of 2.52-2.60,translucent to subtranslucent,and the colour is red,white,pink and seldom yellow.Laos stones consist of kaolinite,dickite and necrite.Phyrophyllite and illite have not been found in Laos stone samples.The Laos stone samples those composed of kaolinite have red or pink colour and less transparence,which are similar to the characteristics of Shanbo stone in larderite.The Laos stone samples those composed of dickite show a light colour and better transperance,which are similar to Kentou stone and Gaos-han stone in larderite.The Laos stone samples those composed of nacrite also are white and translucent.The Laos stones are similar to Gaoshan group of larderite in their mineral components.However,there is an obvious difference between them.Kaolinte containing in most samples is the most important feature of Laos stone,which is different from dickite containing in most larderites.NIR could be a convenient and nondestructive testing method for identifying Laos stones.Colour fading of Laos stones has been said.Fading test for some Laos stones,however,demonstrates that most samples do not fade after lighting,and the colour of some Laos stones being lighter may be attributed to the water containing on the surface of the stones.