Two other nonsilicate minerals frequently found in sedimentary rocks are halite and gypsum. Both minerals are commonly found in thick layers that are the last vestiges of ancient Seas that have long since evaporated(Figure 2.24). Like limestone, both are important nonmetallic resources. Halite is the mineral name for common table salt (NaCl). Gypsum (〖Caco〗_4 〖2H〗_2 O), which is calcium sulfate with water bound into the structure, is the mineral of which plaster and other similar building materials are composed.