The gypsum was deposited in the early Cretaceous Period around 120 million years ago in a lagoonal environment with restricted water flow. Gypsum was formed as the lagoonal waters evaporated and hence is an evaporite mineral. Giant sauropod dinosaurs frequented these lagoons, and numerous footprints of these gigantic animals have been preserved in the sedimentary layers. Crocodile fossils, including teeth and a complete skull, have also been found here. The mineral celestine, containing strontium, is also found.
Strontium is used to make pyrotechnics.
Geologically, the strata in which the gypsum is found is called the DeQueen Formation of the Trinity Group of rocks of the Lower Cretaceous. The physical geology students got a first-hand view of the importance of geological science to our modern way of life and of the efforts of Jim Hardie to restore the mined land. We also were treated to the sight of a newly uncovered sauropod footprint and were able to hunt for minerals and fossils in the mine area.