The Desert rose is made of gypsum crystals in connection with sand. The chemical formula is CaSO4 * 2H2O. The hardness is about 1.5 to 2.
Desert roses crystallize, because of the gypsum crystals in the monoclinical crystal system. There are sulfatic solutions which crystallize near the surface and form these aggregates with the desert sand. So it is the structure of the gypsum crystals.
The process only takes place in desert areas, so we can find desert roses in the Sahara and in the Southwest of the USA. There exist little stones and also stones which are several meters high. The reason of the name is firstly that we find the Desert rose in deserts and the second syllable is because of the form.
Desert roses consist of many wafers which are one in another and which have got a round form. At the each they are thin and they become thicker in the middle. Desert roses are redbrown, but bright.