Igneous Petrology – Origin of Granite Rich in Quartz and Feldspar Granite used as a durable building stone is characteristically composed of quartz and feldspar with mica/other accessories. From which rock class is such granite obtained based on its mode of formation?

Introduction:
Granite is a ubiquitous dimension stone in construction. Identifying its rock class helps predict physical properties like strength, durability, and weathering behavior, and informs quarrying techniques and block stability assessments.

Given Data / Assumptions:

• Granite composition: quartz + feldspar with mica/other accessory minerals.
• Texture: phaneritic (coarse-grained), indicating slow cooling.
• Geologic origin: deep-seated crystallization from molten magma.

Concept / Approach:

Granite forms by slow cooling of silicic magma, producing large interlocking crystals. This igneous origin explains its high compressive strength, low porosity, and good polish—properties valued in construction and cladding.

Step-by-Step Solution:

Verification / Alternative check:

Petrology references classify granite as a felsic intrusive igneous rock (plutonic), distinct from sedimentary or metamorphic origins.

Why Other Options Are Wrong:

Sedimentary and evaporite categories do not match granite’s mineralogy/texture; metamorphic rocks like gneiss may resemble granite but have foliation and a different genesis.

Common Pitfalls:

Confusing gneiss with granite; assuming any crystalline texture implies metamorphism rather than intrusive igneous origin.

Final Answer:

Igneous rocks (crystallized from magma)