Dehydration rates for transformation of gypsum to bassanite at 24 °C and ∼0.7 Pa PH2O. Rates for powdered (<45 μm) to granular (180–425 μm) samples are after Vaniman and Chipera (2006; intermediate curves are for 45–75 and 75–180 μm). Longer dehydration rates are for solid centimeter-scale (2 to 3 g) samples of satin spar (Wildhorse Mesa, Utah = crosses), single selenite crystals (Bingham, New Mexico = diamonds), and nodular evaporite (Todilto formation, New Mexico = triangles). The larger solid samples were run as duplicates and variation in duplicate rates represents variation between sample splits.
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