Igneous Rocks

Andesite Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Aphanitic (fine-grained), sometimes porphyritic

• Composition: Intermediate

• Essential Minerals: Plagioclase, amphibole, pyroxene

• Location Found: Lava flows, volcanic necks

• Intrusive/Extrusive: Extrusive, volcanic

• Relative Rate of Solidification: Fast (moderate cooling rate)

Basalt Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Aphanitic, vesicular, sometimes porphyritic

• Composition: Mafic

• Essential Minerals: Pyroxene, plagioclase, olivine

• Location Found: Lava flows, dikes, sills

• Intrusive/Extrusive: Extrusive, Volcanic

• Relative Rate of Solidification: Fast

Diorite Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Phaneritic (coarse-grained)

• Composition: Intermediate

• Essential Minerals: Plagioclase, amphibole, biotite

• Location Found: Batholiths, laccoliths

• Intrusive/Extrusive: Intrusive, Plutonic

• Relative Rate of Solidification: Slow

Gabbro Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Phaneritic

• Composition: Mafic

• Essential Minerals: Pyroxene, plagioclase, olivine

• Location Found: Dikes, sills, batholiths

• Intrusive/Extrusive: Intrusive, Plutonic

• Relative Rate of Solidification: Slow

Granite Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Phaneritic

• Composition: Felsic

• Essential Minerals: Quartz, feldspar (orthoclase), plagioclase, biotite

• Location Found: Batholiths, laccoliths

• Intrusive/Extrusive: Intrusive, Plutonic

• Relative Rate of Solidification: Slow

Obsidian Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Glassy

• Composition: Felsic (despite dark color)

• Essential Minerals: No crystals — volcanic glass (silica-rich)

• Location Found: Lava flows, lava domes, margins of rhyolitic flows

• Intrusive/Extrusive: Extrusive, Volcanic

• Relative Rate of Solidification: Extremely rapid (quenched)

Pegmatite Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Pegmatitic (very coarse-grained)

• Composition: Felsic

• Essential Minerals: Quartz, K-feldspar, muscovite, rare minerals

• Location Found: Dikes, edges of batholiths

• Intrusive/Extrusive: Intrusive, Plutonic

• Relative Rate of Solidification: Very slow (but in fluid-rich conditions)

Peridotite Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Phaneritic

• Composition: Ultramafic

• Essential Minerals: Olivine, pyroxene, little to no plagioclase

• Location Found: Mantle xenoliths, plutonic intrusions

• Intrusive/Extrusive: Intrusive, Plutonic

• Relative Rate of Solidification: Slow

Pumice Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Vesicular, frothy

• Composition: Felsic

• Essential Minerals: Glassy matrix, some quartz and feldspar

• Location Found: Pyroclastic flows, explosive eruptions

• Intrusive/Extrusive: Extrusive, Volcanic

• Relative Rate of Solidification: Very rapid with gas expansion

Rhyolite Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Aphanitic, often porphyritic

• Composition: Felsic

• Essential Minerals: Quartz, K-feldspar, plagioclase, biotite

• Location Found: Lava flows, volcanic domes

• Intrusive/Extrusive: Extrusive, Volcanic

• Relative Rate of Solidification: Fast

Scoria Texture(s), Composition, Essential Minerals, location Found, intrusive/extrusive, solidification rate

• Texture(s): Vesicular

• Composition: Mafic to intermediate

• Essential Minerals: Pyroxene, plagioclase, olivine

• Location Found: Cinder cones, lava flows, pyroclastic flows

• Intrusive/Extrusive: Extrusive, Volcanic

• Relative Rate of Solidification: Rapid with gas expansion