Igneous Rock Classification

Texture vs. composition

 

 

Felsic

Intermediate

Mafic

Ultramafic

Aphanitic

fine grain

Rhyolite

Andesite

Basalt

Conditions needed to produce ultramafic flows do not exist in nature at this time.

 Intermediate

 

Dacite

Diabase

 

Phaneritic

coarse grain

Granite

Diorite

Gabbro

Peridotite

Glassy

Obsidian

     

Frothy

Pumice

 

Scoria

 

 

It is important to note that there are many, many intermediate steps between these main divisions. Geology is a science full of "shades of gray," and the naming of igneous rocks is certainly no exception.