Marble, which is widely used as a building and sculptural stone, belongs to which category of rocks?

Introduction / Context:
Rocks are classified into three major groups based on their origin: igneous, sedimentary, and metamorphic. Marble is a well known rock used in buildings, monuments, and sculptures. This question tests whether you can correctly identify the rock category to which marble belongs, based on how it forms in nature.

Given Data / Assumptions:

• The options are sedimentary, igneous, metamorphic, or none of these.
• Marble is known to be derived from another rock type by transformation under heat and pressure.
• Basic understanding of rock formation processes is assumed.

Concept / Approach:
Sedimentary rocks form by the deposition and lithification of sediments, such as sandstones and limestones. Igneous rocks form by solidification of molten magma or lava, such as granite and basalt. Metamorphic rocks form when existing rocks are transformed under heat, pressure, and chemically active fluids, without melting into magma. Marble is formed when limestone (a sedimentary rock composed mainly of calcite) is subjected to high temperatures and pressures, typically during regional metamorphism or contact metamorphism. The calcite grains recrystallise, producing a dense, crystalline rock called marble. This clearly places marble in the metamorphic rock category, not sedimentary or igneous.

Step-by-Step Solution:

Verification / Alternative check:
Geology textbooks categorise common metamorphic rocks and list marble as a typical non foliated metamorphic rock derived from limestone or dolostone. They describe marble as consisting of interlocking calcite crystals and often mention its use in art and architecture. In contrast, lists of sedimentary rocks include limestone and sandstone, and lists of igneous rocks include granite and basalt, not marble. This consistent classification confirms that marble belongs to the metamorphic category.

Why Other Options Are Wrong:

Sedimentary rock is wrong because marble is produced by metamorphism of sedimentary limestone; the original rock is sedimentary, but after transformation it becomes metamorphic.

Igneous rock is incorrect because marble does not form from cooling magma or lava; there is no complete melting step in its formation.

None of these categories is wrong because marble clearly fits into the metamorphic category, so the option suggesting none is not appropriate.

Common Pitfalls:
Students sometimes confuse marble with limestone because they share similar chemical composition (mainly calcium carbonate). Another pitfall is forgetting that metamorphic rocks are named after their parent rocks in many cases, but are not the same rock type. To avoid confusion, remember that limestone is sedimentary, while its metamorphosed product marble is a metamorphic rock. This distinction helps in many geology questions.

Final Answer:
Therefore, marble is classified as a metamorphic rock.