I have never seen a piece quite like this...This is a fascinating mineralogical oddity. The form of the white crystal is obviously that of celestine, which has been altered. In fact, on the underside, are some very light blue primary (original) celestine crystals along with minor dark purple fluorite.The celestite had evidently grown upon the fluorite, and some remains attached. Even for the pseudomorph collectors, this one is definitely different. NOTE: NOT ZINN. FROM THE TOM WIESNER FLUORITE COLLECTION (a major Illinois stash), part of which I got at the same time. 5.3 x 5.8 x 4.8 cm