Petrology Basics – Rock formed by solidification of molten magma is called what? Choose the correct name for the rock type that originates from the cooling and solidification of molten material (magma or lava), forming crystalline or glassy textures.

Introduction / Context:
Geology classifies rocks by their origin: deposition and lithification, thermal and pressure transformation, or direct solidification from molten material. Recognizing these categories is essential for civil engineering, as rock type influences strength, durability, weathering, and suitability for aggregates and building stones.

Given Data / Assumptions:

• Original material is molten (magma beneath surface or lava at surface).
• Solidification forms an interlocking mineral matrix.
• No subsequent major alteration implied in the naming.

Concept / Approach:

Igneous rocks crystallize from magma or lava. Slow cooling at depth yields coarse-grained intrusive rocks (for example, granite); rapid cooling at or near the surface produces fine-grained extrusive rocks (for example, basalt). Sedimentary rocks form by deposition, compaction, and cementation of particles or precipitation of minerals. Metamorphic rocks arise from transformation of pre-existing rocks under heat and pressure without melting.

Step-by-Step Solution:

Verification / Alternative check:

Field identification guides correlate textures (phaneritic vs aphanitic, porphyritic) with igneous origin; laboratory thin-section studies confirm interlocking crystal growth patterns.

Why Other Options Are Wrong:

Sedimentary/metamorphic definitions do not involve primary melt solidification; “none” contradicts standard geologic classification.

Common Pitfalls:

Confusing volcanic tuffs (consolidated ash) with sedimentary processes; assuming any crystalline rock is metamorphic.

Final Answer:

Igneous rock