The `montana` data set contains 229 samples of the concentration (in ppm) of five minor elements \([Cr, Cu, Hg, U, V]\) in coal ashes from the Fort Union formation (Montana, USA), in the Powder River Basin.
The five measured elements form a fully observed subcomposition of a much larger chemical composition. Since the data are given in parts per million and all concentrations were measured, a residual component could in principle be added to close the compositions to \(10^6\).
montanaAn object of class data.frame with 229 rows and 6 columns.