Desert rose

Desert rose

Minerals and rocks

Published in A.C. McLean, C. D. Gribble, Geology for Civil Engineers, 2017

Gypsum and its associated mineral, anhydrite, are called evaporites, being formed by precipitation of salts from sea water that has evaporated. These evaporite deposits are common in rock formations of Permo-Trias age. In desert regions, gypsum may be found on the surface of the desert as clusters of flat crystals called desert roses. Salt-flats (sabkhas or sebchas) are widespread in desert regions (see Section 2.2.4), particularly on the coast, and the engineer must be wary of using any such material in building works. Gypsum is mined throughout the world and has many uses; for example ‘panelling’ made of crushed gypsum (gyproc) is widely used in buildings for inner wall claddings because of its excellent fire-resistant and soundproofing qualities. Calcium sulphate is also used as plaster of Paris.

Paleosols and weathering leading up to Snowball Earth in central Australia

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Journal Information

Published in Australian Journal of Earth Sciences, 2021

G. J. Retallack

The Loves Creek and Johnnys Creek formations preserve evidence of a variety of evaporite minerals: halite hopper casts, gypsum sand crystals, and clear anhydrite (Klaebe et al., 2017; Schmid, 2017; Southgate, 1989). Original halite has not been recorded, but the upper Loves Creek Formation has cubic to triangular casts in siltstone with hopper-like pyramidal hollows on cube faces and internal zoning of bowed-in faces. Limpid tabular crystals of gypsum and anhydrite are rare in red siltstones of the Johnnys Creek Formation (Figure 2e, f). There are also small radiating crystal clusters of unferruginised, poikilotopic, crystals (Figure 5e), commonly called ‘sand crystals’ or ‘desert roses’ (Retallack, 2019).

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Minerals and rocks

Paleosols and weathering leading up to Snowball Earth in central Australia