Gemmological Study on Qingtian Stone from Zhejiang Province

Lanhuading, Lanhuaxing, Ziluolan and Shanpaolü, the typical varieties of Qingtian Stone,are studied on their mineral compositions and mineral association by electron microprobe analysis, X-ray powder diffraction analysis, infrared absorption spectroscopy and so on. The following conclusions are drawn: First, the classification of Qingtian Stone from Zhejiang Province based on its mineral association characters shows that Lanhuading belongs to the corundum pyrophyllite type; Lanhuaxing and Ziluolan belong to the dumortierite and alusite pyrophyllite type; and Shanpaolü is mainly composed of mica, not belonging to the pyrophyllite type. Second, the dumortierite-andalusite-pyrophyllite type Qingtian Stone (Lanhuaxing and Ziluolan) has complex mineral association: the yellow matrix is mainly composed of pyrophyllite with a little illite, quartz and other minerals; the blue or purple part in the stone is dumortierite; the light white and rosy spots is andalusite; the achromatic and transparent spot is dickite; and the blue part in corundum pyrophyllite type is composed of microcrystaline corundum. And finally, it is stressed that Shanpaolü is not composed of pyrophyllite at all. Its main mineral is mica, with a little quartz, pyrite, andalusite, illite and so on. Therefore, it should be a new variety of caved stone. Its vivid green is caused by Cr.