How old is a gypsum desert rose?
Gypsum roses are very common in arid zones throughout the world where there is an abundance of calcium in the groundwater and dissolved sulphate ion – probably from pyrite decomposition. Gypsum roses form in soft sandy sediments at depths of up to 3 or 4 metres, usually in drainage depressions such as perennial lake beds, inter-dune playa lakes, or broad floodplains. Usually old shallow marine sedimentary rocks are present nearby – these are the source of the calcium and sulphur to make gypsum. The gypsum crystallises into roses is there is a constant supply of groundwater, and if the sediment has a high porosity and permeability. The time taken to form gypsum roses would be measured in hundreds to thousands of years, depending upon the concentration of gypsum in the groundwater, and the right conditions to force the gypsum out of solution (usually related to alternating periods of wet and dry which recharge the water table and subsequently result in increased concentration of gypsum t
