The structure was determined by direct methods. As proposed by Frost et al., Uranyl pentagonal dipyramids share edges with each other, and are then connected to uranyl hexagonal dipyramids on both sides. The hexagonal dipyramids then link with phosphate tetrahedra to form sheets that connect to adjacent pentagonal chains. The phosphate tetrahedra holding the uranyl chains together display an up-up-down-up-up-down, same-same-opposite orientation (uuduudSSO). Two formula units of the unit cell contain three UO2O5 pentagonal dipyramids, two UO2O5 hexagonal dipyramids, and three PO4 tetrahedra. The Ba(1) site is in 11-fold coordination with oxygen atoms from UO2 polyhedra, and Ba(2) site is in tenfold coordination with UO2 ions and H2O. Also included in the structure of bergenite are hydrogen bonded water molecules, with the network displaying very weak to strong H-bonds. The inconsistency of the bonds originally caused confusion as to whether it was H2O or OH within the mineral, but further observations of Raman spectra proved it to be water. It is the placement of the water molecules that determines the stability of the structure. The positions of the hydrogens in the unit cell remain undiscovered. Bergenite forms as a dark yellow crust with well-developed, small thin needle-like crystals. An original description of bergenite is the orthorhombic symmetry and a density greater than 4.1 g/cm3. Phosphuranylites usually precipitate from solution containing uranium, phosphorus, potassium, and calcium. Most phosphuranylite, and all bergenite specimens, are generated from the waste of various mines. This is a low-temperature and often low-pressure process. Bergenite occurs in fractures of quartz, muscovite, and plagioclase, especially along cleavage planes. Bergenite was first discovered at a now deserted mine dump of the SDAG Wismut shaft 254 in Mechelgrun, Vogtland Mining District, Saxony, Germany near the city of Bergen, Lower Saxony. Other samples have also been found in uranium deposits in the Black Forest, Germany, and in graphitic uranium ore in South Korea. Uranyl phosphates are looked at for environmental concerns, for they are related to hydration-oxidation of used nuclear fuel.