Igneous rock classification schemes
QAP for volcanic rocks
Use this diagram for rocks with a distinct porphyritic or volcanic texture.
QAP for plutonic rocks
This diagram is for plutonic rocks containing quartz or alkalki feldspar. If the rock plots very close to plagioclase, it is more appropriate to use a diagram for mafic rocks
Pl-Px-Ol for mafic rocks
This diagram is the entry diagram for mafic rocks lacking significant hornblende. However, use of the Pl-Opx-Cpx diagram
Pl-Opc-Cpx for mafic rocks
Use this diagram to distinguish between gabbro and norite, or if your rock is mostly plagioclase and pyroxene with little to no olivine or hornblende.
Pl-Px-Hbl for mafic rocks
Use this diagram if your mafic rock contains hornblend.
Ol-Opx-Cpx for ultramafic rocks
Use this diagram for rocks with less than 10% plagioclase that do not contain hornblende.
Ol-Px-Hbl for ultramafic rocks
Use this diagram for rocks with less than 10% plagioclase that do contain hornblende.
Simplified Igneous Rock ID
For identifying hand samples.
Metamorphic Diagrams
Metamorphic Facies
Use this diagram to distinguish the P-T conditions of metamorphic facies.
Stability diagram for Al2SiO5 polymorphs.
Metapelite facies
Common minerals for each metamorphic facies of rocks with a pelitic protolith.
Metabasite facies
Common minerals for each metamorphic facies of rocks with a basaltic protolith.
Metagranitoid facies
Common minerals for each metamorphic facies of rocks with a granitic protolith.
Three Types of Metamorphism
Simplified names of metamorphic rocks by grade, protolith, and type of metamorphism.