Complex sentence: Solutional caves or karst caves are the most frequently occurring caves and such caves form in rock that is soluble, such as limestone, but can also form in other rocks, including chalk, dolomite, marble, salt, and gypsum.
Split into simpler sentences: Solutional caves or karst caves are the most frequently occurring caves and such caves form in rock that is soluble. Most occur in limestone, but they can also form in other rocks including chalk, dolomite, marble, salt, and gypsum.