Which metamorphic rock is formed from limestone under heat and pressure?

• A. Granite
• B. Sandstone
• C. Marble
• D. Basalt

Answer: (C)

Metamorphism is the process by which existing rocks are transformed by heat and pressure into new rocks with different textures and properties. Limestone, a sedimentary rock made mainly of the mineral calcite, when buried and exposed to elevated temperatures and pressures, recrystallizes its calcite grains into a new, interlocking crystal structure. That transformation yields marble, a non-foliated metamorphic rock known for its dense, uniform crystalline texture and often smooth appearance. The other rocks mentioned come from different origins: granite and basalt are igneous rocks formed from cooled molten material, and sandstone is a sedimentary rock made from cemented sand grains. Marble specifically forms from limestone under heat and pressure.