Mineralogical Characteristic of “Laos Stone” with Main Mineral Component Dickite

"Laos stone" is very similar to "Shoushan stone" in appearance.However, the price of "Laos stone" is much lower than that of "Shoushan stone" since its large production,which has brought a severe impact to the market of "Shoushan stone".Optical microscope, Fourier transform infrared spectrometer(FTIR), X-ray diffraction (XRD), laser Raman spectroscopy (LRM), scanning electron microscopy (SEM) and electron probe micro analysis (EPMA) were applied to study its mineralogical characteristics.The XRD results showed that the main mineral component of samples in different colour(red, black and white)is dickite (type 2M1).The crystallinity of dickite is poor, while some dickites forming hexagonal-plate with different sizes.Minor nacrite and kaolinite are also detected.SEM and LRM testing results revealed secondary mineral components in "Laos stone" include hematite, rutile, svanbergite and feldspar.Svanbergite is the main composition of "radish striae "and occurs in fragments or net veins,whose transparency and luster are different from the basic part of "Laos stone".The EPMA result showed that the Fe is enriched in the red "Laos stone".A majority of hematite shows good crystallinity with tetragon and hexagon appearance.The hematite being disseminated structures commonly surrounds the hematite crystal or distributes in the cracks of "Laos stone" and deepens the red colour.