Sandstone, which is mainly composed of sand sized mineral grains, belongs to which major type of rock?

Introduction / Context:
Geology divides rocks into three major types based on how they are formed: igneous, sedimentary, and metamorphic. Sandstone is a very common rock used in buildings and seen in many natural landscapes. This question checks whether you know the correct category of sandstone among the given options. Understanding rock types is important for earth science, geography, construction, and natural resource studies.

Given Data / Assumptions:
– The rock in question is sandstone.
– Sandstone is described as being composed of sand sized mineral grains.
– Options list Calcareous Rock, Igneous Rock, Metamorphic Rock, and Sedimentary Rock.
– We assume standard geological definitions where sandstone is formed from compacted sand deposits.

Concept / Approach:
Sedimentary rocks form from the accumulation and consolidation of sediments such as sand, silt, clay, or biological material. These sediments are deposited by wind, water, or ice and later compacted and cemented into rock. Sandstone is a classic sedimentary rock formed when sand sized particles, often quartz, are compressed and cemented over time. Igneous rocks form from the cooling and solidification of molten magma or lava, examples being basalt and granite. Metamorphic rocks form when existing rocks are transformed by heat, pressure, or chemically active fluids, such as gneiss or marble. Calcareous rock is a descriptive term for rocks rich in calcium carbonate, like limestone, but it is not one of the three main genetic categories. Among the options, sedimentary rock is the correct category for sandstone.

Step-by-Step Solution:
Step 1: Recall that sandstone is made from compacted and cemented sand grains deposited in layers. Step 2: Recognise that rocks formed from deposited and consolidated sediments are called sedimentary rocks. Step 3: Note that igneous rocks form from cooled magma or lava, not from loose sand grains. Step 4: Remember that metamorphic rocks are created when existing rocks are altered by heat and pressure. Step 5: Conclude that sandstone belongs to the sedimentary rock category.

Verification / Alternative check:
Geography and geology textbooks usually present a table of rock types and list sandstone under sedimentary rocks, along with shale, conglomerate, and limestone. Diagrams showing rock cycles also label sandstone as a sedimentary product of weathering, erosion, deposition, and lithification of sand. Igneous rocks are shown forming directly from magma, and metamorphic rocks forming from alteration of existing rocks, which does not match the way sandstone forms. These references confirm that sandstone is sedimentary.

Why Other Options Are Wrong:
Calcareous Rock: This term describes rocks rich in calcium carbonate such as limestone, but it is not one of the three fundamental formation based rock classes, and sandstone may or may not be calcareous.
Igneous Rock: Igneous rocks form from molten magma or lava; sandstone, which comes from lithified sand, does not fit this origin and so is not igneous.
Metamorphic Rock: Metamorphic rocks arise when existing rocks are transformed under heat and pressure; sandstone could become a metamorphic rock such as quartzite, but sandstone itself is not metamorphic.

Common Pitfalls:
Some students confuse sandstone with quartzite, which is a metamorphic rock derived from sandstone. Others may see the term calcareous and think it is a main category like sedimentary, even though it is only a compositional description. To avoid these errors, focus on the formation process: sandstone is literally sand that has turned into stone through sedimentary processes, so it is a sedimentary rock. Remembering this simple link makes classification questions much more straightforward.

Final Answer:
Sandstone is classified as a Sedimentary Rock because it forms from compacted and cemented sand sized sediments.