Which rock is a chemical sedimentary rock?

• A. Rock Salt
• B. Sandstone
• C. Shale
• D. Conglomerate

Answer: (A)

Chemical sedimentary rocks form from minerals that precipitate from solution, rather than from cemented fragments of other rocks. Rock salt is a classic example: it forms when saline water evaporates and the dissolved salts crystallize out as solid halite, building up evaporite deposits. This precipitation process is chemical, not mechanical. In contrast, sandstone, shale, and conglomerate are clastic rocks, made from bits of preexisting rocks and minerals that were transported, deposited, and lithified as a mosaic of grains. So rock salt stands out as the chemical sedimentary option because its formation relies on mineral precipitation from solution during evaporation.