Gypsum   Red River Floodway, Manitoba, Canada. 4.5 x 3 x 2.7 cm ball with one excellent, gemmy swallowtail twinned crystal. Minor rub on small crystal in the ball. This example is a complete floater (having no points of contact to matrix or anything else) and slightly yellower than most examples.  Exceptional luster and form.  Views great from any direction. This one is better than most small examples of this material. These have become uncommon due to their not being mined for currently. I think they are among the finest selentite gypsums available to the collector. $45