黄河矿的一种特殊双晶的发现及其倒易点阵特征

A SPECIAL TWINNING OF HUANGHEITE-(Ce) AND ITS RECIPROCAL LATTICE

本文用转靶四圆单晶衍射仪首次发现黄河矿(BaCe(CO_3)_2F,R3m)的一种特殊类型的双晶,其双晶轴平行c轴,双晶面∥(0001)。发现在晶体中存在着的所有衍射点均符合-h+k+l=3n或h-k+l=3n的衍射条件。这种特殊类型的双晶因其光率体对称轴完全重合,无法凭借光学手段发现。

A special twinning of huangheite-(Ce) (BaCe(CO3)2F, R3m), in which twin plane and composition plane are parallel to (0001), was first discovered by au-thors by means of RASA-5RP four-circlesingle crystal diffractometer. Two kinds of reflection conditions of - h + k+l=3n and h - k+l=3n were observed in one crystal simultaneously. These special reflection conditions should be caused by a twinning. This particular twinning could not be found by means of a polarizing microscope because huangheite-(Ce) is a uniaxial mineral. The optic axes of two individuals of twinning coincide with each other.