andesite (M<35) F1 F2 tephriticphonolite phonolitictephrite foid-bearingtrachyte foid-bearinglatite phonoliticfoidite tephriticfoidite tephrite phonolite 60 10 10 50 35 65 90 90 F A P IUGS ClassificationVolcanic/Aphanitic Rocks2b. Volcanic rocks with feldspathoid F = feldspathoid (foid)A = alkali feldsparP = plagioclase feldspar F1. foid-bearing alkali feldspar trachyteF2. foidite
Olivine Modal %   

Mafic Mineral %   


IUGS Chart 2d. FAP. IUGS diagram for naming volcanic/aphanitic igneous rocks with felspathoid present. Names are based on the relative modal proportions of feldspathoid (F), alkali feldspar (A), and plagioclase feldspar (P). This is a combination of the bottom halves of charts 2a and 2b on one diagram with a Mafic Mineral % slider and an Olivine Modal % slider slider. Use the Olivine Modal % slider to see the classifications for rocks with olivine > 10%. Use the Mafic Mineral % slider to see the andesite classification change to basalt for rocks with M>35%.

For quartz-bearing volcanic/aphanitic rocks click here:
For the full IUGS QAPF Volcanic chart click here: