The Great Salt Plains in Alfalfa County, in northwestern Oklahoma, the United States, is the only place in the world where hourglass-shaped selenite crystals are found. Millions of years ago this area was covered by a large inland sea. The sear was eventually cut off and the water evaporated away, leaving behind thick layers of salt that were subsequently covered by dirt and erosion from surrounding mountain ranges. As groundwater rises to the surface through the salt-saturated sand, it takes salt along with it and deposits them on the surface as a thin crust. It is the concentrated saline solution combining with gypsum that promotes the growth of selenite, a crystalline form of gypsum. These crystals are found buried only a few feet below the surface, under an area that’s 11,000 square miles in size.
Selenite crystals dug up from the lake bed. Photo credit: Neal/FlickrRead more »
© Amusing Planet, 2015.