The `petrafm` data set contains 100 classified volcanic rock samples from Ontario (Canada). The three-part composition is
\([A: Na_2O + K_2O;\ F: FeO + 0.8998\,Fe_2O_3;\ M: MgO]\)
Rocks from the calc-alkaline magma series (25 samples) can be distinguished from those of the tholeiitic magma series (75 samples) using an AFM diagram.
petrafmAn object of class data.frame with 100 rows and 4 columns.