Gypsum     Mapimi, Durango, Mexico.  Ex. Dr. Steve Chamberlain collection, prev. Ralph Lapham collection.  This is an old specimen which is very interesting due to what is inside.  Running most if the crystals length is an inclusion (negative crystal) which is approximately 2 millimeters wide and 5.5 cm long.  The entire crystal measures 10 x 2 x .7 cm.  It is doubly-terminated and striated along its narrowest faces.  Even the inclusion has striations!  Little marks here and there on the surface of the crystal (I’m not convinced that these are damage even with magnification).  A fine piece for…80$