昌化地开石次生矿风化层矿物学特征

Mineralogical characteristics of the weathered layer of Changhua secondary dickite stone

运用FTIR、SEM和EDS等分析方法对浙江昌化地开石次生矿中俗称"昌化田黄"的风化层矿物组成、微观形貌及化学成分变化进行了系统研究,结果表明,风化层的主要矿物组成为高岭石族矿物,含有铁质及钙镁质副矿物。与未风化新鲜层相比,风化层的组成矿物因溶蚀作用及颗粒间隙铁质矿物充填作用连结成片,晶体边界模糊不清。部分样品风化层表面附着Fe、Mn质矿物,Fe、Ca等元素含量普遍高于未风化层。风化表层与未风化新鲜层显微结构显示出明显的差异,沿风化剖面由表及里Fe、Ca元素含量逐渐降低,二者为"昌化田黄"经历次生风化作用的显著表征。而次生风化层中石英矿物的出现以及含Mn质矿物的表层附着,可为"昌化田黄"与寿山田黄的产地鉴别提供依据。

Using FTIR,SEM and EDS,the authors systematically studied the mineral composition,micro-characteristics and the variation of chemical composition of the weathered layer of Changhua secondary dickite stone,which is usually called Changhua Tianhuang. The result indicates that the main mineral composition of the weathered layer is kaolinite-group minerals,consisting of some Fe,Ca,Mg-bearing accessory minerals. Compared with those of the inner layer,the mineral crystals of the surface weathered layer have a blurred boundary and shape,due to the dissolution and the filling of Fe-bearing minerals. The difference of micro-characteristics between inner and surface layer as well as the decreasing of Fe,Ca from weathered layer to unweathered layer demonstrates the weathered progress of the Changhua secondary dickite stone. The appearance of quartz in the weathered layer and the attachment of the Mn-bearing mineral can help identify the origin of Changhua and Shoushan Tianhuang stone.