Which pair are metamorphic rocks?

• A. Granite and Basalt
• B. Sandstone and Limestone
• C. Marble and Slate
• D. Coal and Shale

Answer: (C)

Metamorphic rocks form when existing rocks are altered by heat, pressure, or chemically active fluids without melting. Marble and slate exemplify this transformation: marble forms when limestone is recrystallized under heat and pressure, producing a hard, crystalline texture. Slate comes from shale that has undergone low-grade metamorphism, developing a fine foliation and the ability to split into thin sheets. The other pairs are not metamorphic: granite and basalt are igneous rocks that crystallize from molten material; sandstone and limestone are sedimentary rocks created by cementation and lithification of grains; coal and shale are also sedimentary, with coal from plant material and shale from clayey sediments.