-Stage 1.4-

Igneous Rocks

Igneous Rock CycleDefinition - Igneous rocks form from the solidification of molten rock (AKA lava or magma)

Lava - molten rock above the ground surface

Magma - molten rock below the ground surface


Igneous Rocks

Previous Step


Next Step


Types of Igneous Rocks

Identifying Igneous Rocks

Igneous Rock Classification

Igneous Rocks

Petrogenesis (Creating Rocks)




Bowen's Reaction Series


Bowen's Reaction Series


Understanding Bowen's Reaction Series

Definitions Used for Identification

(Click on the images for a larger image)


     Visible Crystals:

Pegmatitic - This is when the crystals in the rock are larger than 1 cm across. This is the most common type of rock where gem stones are found due to the large crystal size.



Phaneritic - This is when crystals are between 1 mm and 1 cm



     Non-Visible Crystals:

Aphanitic - This is when there are no visible crystals in the rock



Porphyritic - This is when the background are not visible but there are large crystals "floating" in the mass



Glassy - This is when there are no visible crystals and the surface is reflective (i.e. like glass)



Vesicular - This is when the rock contains lots of air holes, causing the rock to be lighter then usual



Pyroclastic - This is when the rock forms from angular pieces of other rocks in a aphanitic matrix (similar to porphyritic but larger/angular crystals/ rock chunks)




Felsic - "light" rocks, contain light colored minerals (Also low temp minerals See Bowen's Reaction Series above) (quartz, Potassium feldspar, micas)



Intermediate - A mixture of felsic and mafic, "salt and pepper" "light and dark" (Potassium feldspar, Sodium Plagioclase, Biotite, Amphibole)



Mafic - "dark" rocks, contain dark colored minerals (Also high temp minerals See Bowen's Reaction Series above) (Pyroxene, Amphibole, Calcium Plagioclase)



Utramafic - "green" rocks, contain green colored minerals (The highest temp on Bowen's) (Olivene)