Sedimentary Rocks Containing Gypsum

Much building material has been derived from two monomineral sedimentary rocks gypsum (composed of hydrated calcium sulfate) and limestone, which consists of calcite (composed mostly of calcium carbonate). Freshwater and seawater contain dissolved calcium carbonate and calcium sulfate. Most limestone and gypsum are formed when, as a consequence of the evaporation of water, calcium sulfate and calcium carbonate precipitate out of the water solutions as either gypsum or limestone. Limestone is also formed as a result of the activity of living organisms. Many sea- and freshwater animals, such as snails, clams, and corals, as well as some water plants, draw... 

Geologic sources of sulfur include primary and secondary sulfide minerals as well as chemically precipitated sulfate minerals. In sedimentary rocks, sulfur is often concentrated. Examples include pyritic shales, evaporites, and limestones containing pyrite and gypsum in vugs and lining fractures. In many cases, these rocks can be both the source of organic matter as well as sulfate for the biogeochemical reduction of sulfate to occur. 

Of the two naturally occurring strontium containing minerals, strontianite (SrGOj) and celestite (SrSO, the latter occurs much more frequently in sedimentary deposits of sufficient quantities to make its recovery practical. Strontianite would be the more useful of the two common minerals, because strontium is used most often in the carbonate form. Gelestite occurs principally as nodules, lenses, beds and materials filling crevices in sedimentary rocks such as carbonates, gypsums, days and evaporites. The economic importance of celestite is con-... 

---