Igneous Textures Quiz

Study Notes

Igneous Textures

Texture: Refers to the size, shape, and arrangement of mineral grains or crystals in igneous rocks.
Glass: Describes rock made of unordered ions, lacking a crystalline structure.
Aphanitic Texture: Characterizes igneous rocks formed at the surface or near the upper crust with rapid cooling, resulting in a very fine-grained appearance.
Vesicular Texture: Identified by the presence of vesicles, which are spherical or elongated openings within the rock.
Phaneritic Texture: Found in igneous rocks that crystallize slowly at depth, showing a coarse-grained texture with visible crystals.
Porphyritic Texture: Features large crystals known as phenocrysts embedded in a matrix of much smaller crystals, indicating different cooling rates.
Phenocrysts: The term for large crystals that stand out in a porphyritic rock.
Glassy Texture: Describes the texture of igneous rocks like obsidian, marked by an absence of crystals, giving a smooth, glass-like appearance.
Pyroclastic Texture: Resulting from the consolidation of rock fragments ejected during explosive volcanic eruptions, forming a mixed-texture rock.
Fragmental Texture: Comprises igneous fragments that have solidified and can be packed, welded, or cemented together.
Pegmatites: Notable for their exceptionally coarse-grained structure, typically formed in the late stages of magma crystallization.
Pegmatitic Texture: Used to describe the very large crystals present in pegmatites, signifying an environment of slow cooling and crystallization.

Description

Test your knowledge on the various textures of igneous rocks. This quiz covers key definitions and characteristics such as aphanitic, vesicular, phaneritic, and porphyritic textures. Deepen your understanding of how cooling rates affect crystal formation in igneous geology.