The Scheme for Igneous Rock Identification

A Brief Tour

Grain size Description Crystal size

Igneous rocks have “Intergrown Crystals”

Intergrown

Intergrown

Intergrown

Not Intergrown

Where it was formed Outside the volcano: Extrusive Inside the Earth: Intrusive Where it was formed

Bubbles? Yes= Vesicular

No=Non-vesicular Bubbles?

Color Neither Light nor Dark Very Light NotVery Light Very Dark Not Very Dark Light Dark Darkest Lightest

Very Light Medium Density Density Light Dense Very Dense

Finding The Minerals Unless you have other information, work in the middle of the rock’s box. Identify the rock.

This is the amount of Potassium Feldspar in the rock.

This is the amount of Quartz in the rock.

This is the amount of Plagioclase Feldspar in the rock.

Use tick marks on a scrap paper to measure the percentage. Potassium Feldspar 25% Quartz 40%

Name a light-colored, fine-grained rock with no bubbles. Practice

Name a coarse-grained, dense rock.

Name a dark colored , dense rock that can be intrusive or extrusive