  For neutrino propagation in matter, we show that the Jarlskog invariant,
which controls the size of true CP violation in neutrino oscillation appearance
experiments, factorizes into three pieces: the vacuum Jarlskog invariant times
two simple two-flavor matter resonance factors that control the matter effects
for the solar and atmospheric resonances independently. If the solar effective
matter potential and the atmospheric effective $\Delta m^2$ are chosen
carefully for these two resonance factors, then the fractional corrections to
this factorization are an impressive 0.04\% or smaller. We also show that the
inverse of the square of the Jarlskog in matter ($1/\hat{J}^2$) is a fourth
order polynomial in the matter potential which guarantees that it can be
factored into two quadratics which immediately implies the functional form of
our approximate, factorized expression.
