A plate of off-white barite crystals on a limestone matrix, from the Linwood Mine, Buffalo, Scott Co., Iowa. This particular material is known locally as "Popcorn Barite," and is brightly fluorescent and phosphorescent. Under short wave UV (254nm) the barite shows a bright blue/white fluorescent response with blue/green phosphorescence. The barite shows a similar fluorescent response under long wave UV (365nm) with dim green phosphorescence. Approximate dimensions are 14 x 10 x 5 cm.