Which rock is formed by metamorphism of existing rocks due to heat and pressure, without melting?

Which rock is formed by metamorphism of existing rocks due to heat and pressure, without melting?

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

Answer: (A)

This item tests understanding of metamorphism in the solid state—how existing rocks are altered by heat and pressure without melting. Marble forms when limestone, a sedimentary rock, is subjected to heat and pressure that cause the calcite minerals to recrystallize, producing a dense, interlocking crystal texture. The rock changes shape and composition while remaining solid, so there’s no melting involved. That solid-state transformation is why marble is classified as a metamorphic rock. In contrast, granite and basalt come from magma that cools and solidifies (igneous), and sandstone forms from cemented sand grains (sedimentary), not through metamorphism.

This item tests understanding of metamorphism in the solid state—how existing rocks are altered by heat and pressure without melting. Marble forms when limestone, a sedimentary rock, is subjected to heat and pressure that cause the calcite minerals to recrystallize, producing a dense, interlocking crystal texture. The rock changes shape and composition while remaining solid, so there’s no melting involved. That solid-state transformation is why marble is classified as a metamorphic rock. In contrast, granite and basalt come from magma that cools and solidifies (igneous), and sandstone forms from cemented sand grains (sedimentary), not through metamorphism.