extrusive (volcanic)

Answer:

Igneous activity that occurs at Earth's surface

intrusive (plutonic)

Answer:

Igneous rock that formed below the Earth's surface

aphanitic texture

Answer:

A texture of igneous rocks in which the crystals are too small for individual minerals to be distinguised with the unaided eye

phaneritic texture

Answer:

An igneous rock texture in which the crystals are roughly equal in size and large enough so that individual minerals can be identified with the unaided eye

porphyritic texture

Answer:

An igneous rock texture characterized by two distictively different crystal sizes. The larger crystals are called phenocrysts, and the matrix of smaller crystals is termed the groundmass

phenocrysts

Answer:

The larger crystals in rocks exhibiting porphyritic texture

glassy texture

Answer:

A term used to describe the texture of certain igneous rocks, such as obsidian, that contain no crystals

pyroclastic (fragmental) texture

Answer:

An igneous rock texture resulting from the consolidation of individual rock fragments that are ejected during a violent eruption

pegmatitic texture

Answer:

A texture of igneous rocks in which the interlocking crystals are all larger than one centimeter in diameter

pegmatites

Answer:

A very coarse-grained igneous rock (typically granite) commonly found as a dike associated with a large mass of plutonic rock that has smaller crystals. Crystallization in a water-rich enviornment is believed to be responible for the very large crystals