Gypsum (var. Hourglass Selenite)

A lustrous, doubly terminated, nearly textbook crystal of gypsum, (var. hourglass selenite).  This crystal was recovered during an excavation project at Willow Creek, near Nanton, Alberta, overseen by Rod Tyson, circa 1992. The occurrence in clay preserved and protected the crystals from weathering. Twinned selenite crystals from Willow Creek show a unique fluorescent response under UV light, producing a bright hourglass-shaped area of zonal fluorescence characteristic of this location. Beautiful and fascinating!