Sodium and Potassium
Na2O and K2O vs. Fe2O3(T)
Most terrestrial rocks are richer
in Na2O than any meteorite. Rocks with >2%
Na2O are probably not meteorites.
Sodium and potassium are both alkali
elements, and all alkali elements are in low concentrations
in meteorites compared to most terrestrial rocks. Rocks
with greater than 0.6% K2O are probably not meteorites.