Tridymite pseudomorphs after wood in virginian lower cretaceous sediments.
Fossil wood composed of tridymite is abundant in Patuxent (Lower Cretaceous) arkose on Hazel Run, Fredericksburg, Virginia. X-ray diffraction studies of the tridymite indicate that it has a disordered structure in which hexagonal close packing predominates. The specimens, which contain trace amounts of aluminum, iron, and other elements, are soft and fibrous, varying from white to shades of brown.