Introduction to Igneous Rocks and Their Textures lec 2

These flashcards cover key vocabulary and concepts related to igneous rocks and their textures discussed in the lecture notes.

Extrusive Rocks

Rocks that form at the surface of the earth, typically characterized by tiny crystals or glass due to rapid cooling.

Phaneritic Texture

A texture of igneous rock where individual crystals are visible to the naked eye.

Aphanitic Texture

A texture of igneous rock that is fine-grained where individual crystals are too small to see without a microscope.

Porphyritic Texture

Igneous rocks consisting of larger crystals (phenocrysts) embedded in a finer-grained matrix (groundmass).

Vesicular Texture

A texture characterized by holes or vesicles left by gas bubbles in lava as it solidifies.

Glassy Texture

A texture in which no crystals form at all, resulting from extremely rapid cooling of lava.

Pyroclastic Texture

Rhyolitic texture formed from the fragmentation of rocks during explosive eruptions, consisting of ash, pumice, and rock fragments.

Crystallinity

The proportion of crystalline material versus glass in the rock.

Equigranular

Rocks that have crystals of approximately the same size.

Inequigranular

Rocks that contain crystals of different sizes.

Pegmatitic Texture

A texture of igneous rocks marked by very large crystals, often larger than one centimeter.

Euhedral Crystals

Crystals that have well-defined, flat faces that reflect their internal crystal structure.

Subhedral Crystals

Crystals that have some well-defined faces but are partially rounded.

Anhedral Crystals

Crystals that lack recognizable faces and have irregular shapes.

Beaded Texture

A texture defined by a specific crystallization relationship, typically between plagioclase and peroxine.

Spinifex Texture

A texture characterized by dendritic or branching crystal forms, resulting from very rapid cooling.

QAPF Diagram

A ternary diagram used for classifying igneous rocks based on their relative proportions of quartz, alkaline feldspar, and plagioclase.

Anorthosite

An igneous rock composed predominantly of plagioclase feldspar, typically over 90%.

Diorite

An intermediate igneous rock with equal amounts of light and dark minerals, commonly observed in subduction zones.

Pegmatite

An igneous rock with excessively large crystals formed from the last volatile-rich cooling of magma.