Igneous Rock Colors

Another characteristic used to help identify igneous rocks is its color.  Igneous rocks are classified based on only 4 colors: mafic, ultramafic, felsic, and intermediate.

 

Below is a table with examples of each color of igneous rock.

Type of color % of Dark Minerals Composition Example Image
Mafic >40% dark minerals No quartz or potassium feldspar is found.  These are your dark green, brown, red, gray and black igneous rocks.  Can have some light color to it.

Mafic

Ultramafic Nearly 100% dark minerals Full of very dark minerals.  These are your rocks that lack light colored minerals.  Doesn't mean they are just black.  It means they are lacking any light colored element.

Ultramaphic

Felsic <15% dark minerals Very light in color, a bunch of quartz, potassium feldspar, very few dark minerals found.  These are your white and pink colored igneous rocks.  

Felsic

Intermediate 15-40% dark minerals In between dark and light in color. There is more plagioclase feldspar.  These are your grayish igneous rocks.  

Intermediate Colored Igneous Rocks

Below is a chart that shows the percentage of silica and oxygen found in igneous rock colors. 

Igneous Rock Color Chart

 

With your groups organize the igneous rock kit into ultramafic, mafic, intermediate and felsic colors.

Now that you understand igneous texture, color, composition, and whether an igneous rock is intrusive or extrusive, it is time to take that knowledge and apply it by identifying some igneous rocks.

SUSD5 Student Igneous Rock Identification lab

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