Similarly, tree stumps submerged in a hypersaline lake of the Lower Cretaceous Purbeck Formation of Dorset, UK, have provided attachment areas on which stromatolites have formed. In the clayey sand a few centimentres below the surface there are these white nodules with sutures between them. These are probably Recent anhydrite nodules like those described in previous literature from the Abu Dhabi area of the Emirates. These are not crumbly and prone to distintegrate as is usually the case and very much resemble ancient nodules of anhdyrite or secondary gypsum. In some ancient sequences where there has been replacement of quartz from the outside and dissolution of the calcium sulphate these can form geodes.
Further study is needed.
At present we have not yet done laboratory studies and cannot even be sure that this is anhydrite and not gypsum. Further into the salt lake the anhydrite is soft and creamy and solid nodules cannot be extracted. Primary gypsum nodules in a modern sabkha on the Mediterranean coast of Egypt. Desert Roses - Gypsum Crystals Large desert roses or gypsum sand crystals in the sand of a supratidal sabkha at Umm Said in eastern Qatar. They split and fan open along these characteristic cleavage planes of gypsum.