In basic geology, granite is an example of which major type of rock based on its origin and formation?

Introduction / Context:
Granite is a very common rock used in buildings, monuments, and countertops, and it is also an important rock type in geology. School level earth science divides rocks into three main groups based on their origin: igneous, sedimentary, and metamorphic. Knowing which group granite belongs to helps students understand the rock cycle and how Earth crust has evolved over time. This question checks whether you can correctly classify granite according to its mode of formation.

Given Data / Assumptions:
• The rock named in the question is granite. • The options list igneous, sedimentary, calcareous, and metamorphic categories. • We assume standard geological classifications taught in school textbooks. • Granite is known for its coarse grained texture and quartz feldspar composition.

Concept / Approach:
Igneous rocks form when molten rock material, called magma or lava, cools and solidifies. If this cooling occurs deep inside the Earth, the rock is called intrusive or plutonic and typically has large visible crystals. Granite is a classic intrusive igneous rock, formed from slow cooling of silica rich magma within the crust. Sedimentary rocks, by contrast, form from deposition, compaction, and cementation of sediments like sand, silt, and organic material. Metamorphic rocks form when existing rocks are changed by heat and pressure without complete melting. Calcareous rocks are rich in calcium carbonate and are usually sedimentary, such as limestone. Since granite originates from cooled magma and shows large interlocking crystals, it is correctly classified as an igneous rock.

Step-by-Step Solution:
Step 1: Recall that igneous rocks are formed by cooling and solidification of molten material. Step 2: Remember that granite is coarse grained and composed mainly of quartz, feldspar, and mica. Step 3: Recognise that such texture and composition are typical of intrusive igneous rocks. Step 4: Check that sedimentary rocks usually show layers or contain fossils, which is not typical for fresh granite. Step 5: Confirm that metamorphic rocks such as gneiss show strong banding and foliation, different from massive granite. Step 6: Conclude that granite is best described as an igneous rock.

Verification / Alternative check:
Geology textbooks and field guides describe granite as a felsic intrusive igneous rock, often forming large batholiths and continental crust foundations. Rock classification charts clearly place granite under igneous rocks, opposite to sedimentary examples like sandstone and limestone and metamorphic examples like schist and marble. In the laboratory, thin sections of granite under a microscope also show interlocking crystals consistent with slow cooling from magma. There is no recognised classification of granite as a sedimentary or purely calcareous rock, which confirms the igneous origin.

Why Other Options Are Wrong:
Option B, sedimentary rock, is incorrect because granite does not form from deposited layers of particles; instead, it crystallises from molten material. Option C, calcareous rock, refers to rocks rich in calcium carbonate such as limestone and chalk, which are usually sedimentary and not granitic in composition. Option D, metamorphic rock, would apply to rocks that have been transformed from pre existing rocks, such as granite changing to gneiss under heat and pressure, but the original granite itself is not metamorphic. These options do not match the well established origin of granite.

Common Pitfalls:
Students sometimes confuse granite with marble or other polished stones used in buildings, assuming that all decorative stones are of the same type. Another common mistake is to treat granite as metamorphic because it can appear in mountainous regions where metamorphism also occurs. It helps to focus on how the rock initially formed rather than where it is found or how it is used. Remembering the simple rule granite equals igneous rock formed from cooled magma is a reliable way to answer similar questions correctly.

Final Answer:
The correct choice is Igneous rock that solidified from magma, because granite is an intrusive igneous rock formed by the slow cooling and crystallisation of silica rich magma deep within the Earth crust.