Mineralogical Study on Cattle-Egg Stone from Shoushan County,Fujian Province

The systematic mineralogical studies are worked on the yellow and black cattle-egg stone samples from Shoushan rivulet of Fujian Province.The parts of the weathering skin(popularly called "skin of the stone"),basal part(popularly called "flesh of the stone") and core part(popularly called "heart of the stone") of the cattle-egg stone samples are tested by XRD,SEM,EDS and bulk-rock analysis respectively.It indicates that the different parts of the cattle-egg stone samples in different colours all mainly compose of pyrophyllite,coexisted by two kinds of polytype of monoclinic and triclinic pyrophyllite,and the average crystal structural formula is Al_4.04[Si_7.89Al_0.11O₂₀](OH)₄.The aggregation of pyrophyllite arranges with no direction,and the crystal size of the single pyrophyllite crystal in the weathering skin is a little bigger than that in the basal part.The colour of the two kinds of the samples are caused by Fe³⁺ cation.What's more, the black sample contains no diaspore,while the yellow one contains it.