Concretion, Sandstone, Naturally Formed, Desert Stone (Approx. 5/8" - 1") 0319 You will receive one stone from the ones pictured in this listing. Size is approximate. Concretions hold the key to understanding diagenesis (i.e., what happens between the time sediments are deposited and when the rock is uplifted and exposed). Concretions can help us understand ground water better - water that we use for drinking and irrigation and need to keep clean. They also provide clues to understanding oil and gas reserves and subsurface carbon dioxide sequestration (to combat global warming) - industries that create well- See more at stonepathtrading.com