Mineralogical Study Of Shoushan Stones

The Shoushan stone is of great reputation at home and abroad for its sleek texture, flowery color and various category. The ore are located in the intermediate-acid volcanic rocks of the Late Jurassic and the Cretaceous period around the hills and villages of Shoushan,Rixi,Huanxi which stauated in north of City Fuzhou. The mineralogy study on the Shoushan stone can provide more gemmoloy dates and information to its exploitation and appliance.Samples collected from four major deposites of Shoushan stone (Dulin/Shanbo/Hukou/Qijiang) in Fujian Province. were studied by optical microscopy(OM), scanning electron microscopy(SEM), Electron probe analysis(EP), X-ray powder diffraction(XRD), infrared spectroscopy(IR), differential thermal analysis(DTA), and thermogravimetry(TG) in physical characteristics; mineral constituent; conformation and internal structure of the main constituent kaolin minerals.The results of OM and SEM in combination with EP analyses determine that Dulin stone and Shanbo stone contain kaolin minerals as a dominant constituent; Hukou stone mainly consist of pyrophyllite, while these two kinds of minerals make up Qijiang stone as the primary compositions. All of these Shoushan stone associated with minor quantities of quartz and little limonite; and little pyrite and rutile exist in Shanbo stone and Hukou stone respectively.The analyses of XRD indicated the prophyllite in stones exist two polymophs, i. e. monoclinic of Qijiang stone and triclinic of Hukou stone; both Duling stone and Shanbo stone are composed of dickite. XRD patterns of QJ stone showed the existence of well-crystallized minerals in which the (003),( 13 1),(131)reflections appeared as medial/intense/weak intensity relationship associated with several characteristic reflections of dickite. These patterns suggested the presence of an intermediate member between well-crystallized dickite and well-crystallized kaolinite. The"Hinckley-type index"of stones from Qijing/Shanbo/Duling is 1.220,1.034,1.057 separately with only a little bit difference.IR and DTA-TG date agree with those from XRD. Dickite of Duling stone and Shanbo stone different from kaolinite-dickite mixed-layer mineral are shown by the position and the relative intensities of the absorption bands in the OH-stretching region (3700-3600cm-1). According to their values of HI, order index(OI) of stones from Qijing/ Shanbo/ Duling are 1.041,0.886,0.995 respectively with declination of order degree. The shape and peak temperature of the main endothermic dehydroxylation peak in the DTA curves also reflected differences in crystallinity and order degree to a certain extent.