Week 3: Igneous Rocks to know

What are the characteristics of Granite and Rhyolite?

Felsic (High silica content)

A major constituent of continental crust

Granite: Intrusive

Rhyolite: Etrusive

What are the characteristics of Andesite and Diorite?

Intermediate (In terms of Silica content)

Associated with volcanism at continental margins

Andesite: Extrusive

Intrusive: Diorite

What are the characteristics of Basalt and Gabbro?

Mafic

Has dark ferromagnesian minerals (High in Iron and Magnesium)-Pyroxene, Amphibole, Olivine

Major constituent of ocean crust, volcanic islands, and continental lava flows

Basalt: Extrusive

Gabbro: Intrusive

What are the characteristics of Peridotite?

ultramafic (very low silica)

Almost entirely ferromagnesian (High in Iron and Magnesium, olivine is most abundant)

Main constituent of the upper mantle

Intrusive (Extrusive is very rare)

What are characteristics of tuff?

Fine-grained

Pyroclastic

Composed primarily of ash

What are characteristics of Volcanic Breccia?

Angular fragments of pyroclastic debris that are cemented together

What are characteristics of Obsidian?

Glassy

Felsic

Has conchoidal fractures

What are the characteristics of Pumice?

Felsic glass

Has abundant vesicles (Many cavities in its surface)