Mineralogical Classification

Rock names are based on texture and mineralogy. There are nine common names to remember, three intrusive rocks are three extrusive rocks. From the most acid to the most basic, the intrusive rocks are:

• GRANITE
• DIORITE
• GABBRO

The corresponding extrusive rock names (with similar composition and mineralogy) are:

• RHYOLITE
• ANDESITE
• BASALT

The remaining names are applied to ultrabasic rocks with very little silica:

• PERIDOTITE (olivine rich)
• PYROXENITE (pyroxene rich)
• ANORTHOSITE (plagioclase feldspar rich)