Discrimination of bassanite and anhydrite III dehydrated from gypsum at different temperatures

Rietveld Quantitative Phase Analysis of OPC Clinkers, Cements and Hydration Products

“…The formations and transformations of the five different phases in the CaSO 4 -H 2 O system have been studied in detail (Christensen et al 2008). The use of RQPA for determining the amounts of gypsum, bassanite and anhydrite in OPC was already demonstrated several years ago (Fullmann and Walenta 2003;Walenta and Fullmann 2004;Seufert et al 2009b). The mineralogy of the sulfate source is very important for the fluidity, setting and hydration of mortars and concretes (Tang and Gartner 1988;Rossler et al 2008).…”

Gypsum, bassanite, and anhydrite at Gale crater, Mars

“…2). Although gypsum, bassanite, and anhydrite are common mineral names, terminology used for Ca-sulfate phases can be complex, particularly in the use of "soluble anhydrite," "g-anhydrite," or "anhydrite III" (e.g., Bezou et al 1995;Carbone et al 2008;Seufert et al 2009) for dehydrated channel structures more similar to bassanite than to common anhydrite (which lacks channel structure and hydrates less readily). In this paper, we refer to the anhydrous structure without channels simply as anhydrite, or "common anhydrite" where there may be some confusion with channel-bearing structures, such as soluble anhydrite, that are more similar to bassanite than to common anhydrite.…”

“…The Moiola and Glover (1965) study has some constraints on rate and amount of transformation, for within one year they describe initial wet growth of centimeter-scale gypsum crystals followed by dry alteration of the crystal surfaces, in which a thin (~60 mm) layer of bassanite occurs between the gypsum core and an outer layer (~500 mm) of common anhydrite, supporting an interpretation of progressive desiccation from the gypsum core to the anhydrite rim. Laboratory experiments heating gypsum for 120 h in air at 85 °C have produced a small percentage (4%) of common anhydrite along with 95% bassanite (Seufert et al 2009); whether geologically longer exposure of gypsum at lower temperatures might also produce common anhydrite is not known. Although MSL data support likelihood of some bassanite formation by desiccation from gypsum, it remains unknown whether prolonged surface exposure at Gale crater might produce common anhydrite as well as bassanite.…”

Rietveld quantitative phase analysis of Yeelimite-containing cements

“…It should be noted that gypsum, bassanite and less-soluble anhydrite-II can be easily distinguished and quantified by RQPA. However, bassanite and highly soluble anhydrite-III can only be distinguished in especial experimental conditions [66] with high-quality laboratory X-ray powder diffraction data. IV) The good accuracy of the analyses can be estimated by the comparison of the XRF results (Table 2) and RQPA results (Table 5).…”