Micromorphic Forms of Soil Gypsum

Geologic gypsum occurs in many crystalline forms, such as saccharoidal (alabaster), satin spar, rose and serenity. Saccharoidal, the most important commercially, resembles lump sugar and occurs as massive beds. Satin spar is fibrous in appearance, has a satin luster, and forms thin discontinuous layers. Rose gypsum growing in arid conditions in clastic sediments sometimes assumes this shape. Serenity is a transparent, often colorless, crystalline variety. The objective of this study was to identify micromorphlogical forms of soil gypsum, i.e. do geologic forms remain in soils. The micromorphlogical forms of soil gypsum were studied from different parent materials, such as eolian, fluvial and residual. In general, pedogenic gypsum does not retain the form of geologic gypsum. Lenticular gypsum is the most common form of pedogenic, but other forms occur. The development of pedogenic gypsum seems to be controlled by rate of formation and, to some degree, by the texture of the soil. The effect of dehydration on crystal form was also investigated.